Interesting thread. Not sure I can help or not, but I can share my insight and thoughts with you.
1. You seem to plan to spend massive sums of money. No probs, it's your choice. But there might be other vehicles worth spending less on, depending on your final goals.
2. Understand the limitations of what you are doing and wanting to achieve. A D2 will always be a fairly large 4x4 with long overhangs front and rear. This means they will always be a bit bulky off road in the UK and likely more prone to damage. Not a problem if you don't mind taking some damage, but worth noting if you are wanting to keep it looking tidy.
3. I'm assuming you are in the UK?
4. A question to you. What are you wanting to achieve? There simply is no ultimate 4x4 setup, as it depends what attributes you are wanting to exploit.
For example, this is a mud truck. They generally are required to wade through very deep water and mud, in large, often open area's. They don't need much in the way of steering lock, or be that stable on uneven terrain or side slopes. i.e. for rock crawling they'd likely be pretty rubbish.
I admit, they often look cool and very 'monster truck' like.
Sedate example:
Extreme example:
Now for rock crawling you want a completely different type of vehicle to a mud truck. You want something much smaller and lighter. Much lower centre of gravity and a lot less lift. What you do want is suspension travel and stability. Short overhangs are good too, where they are largely unimportant on a mud truck.
Note how much smaller less lifted they are compared to the mud trucks.
So why am I showing you these?
Basically to highlight the different solutions needed for different off road terrain and disciplines.
In the UK we don't tend to have either extremes of mud pits or pure rock crawling. But what we do get is a lot of muddy uneven terrain with plenty of slopes, hills and ditches. And lots of trees!
This means you probably want a vehicle somewhere in between. i.e. HIGH stability is vitality important. Suitable wading ability, but maybe not on a giant scale nor lifted to extremes.
I'm not telling what you should do, just trying to give some food for thought....
5. Actual intended use. Highly related to my previous point. I see you have mentioned green laning. Now lets be brutally honest, for something like 95% of all green lanes in the UK for maybe 95% of the time, a stock Discovery on AT's is probably more than capable. You do NOT need an extreme truck for green lanes.
I'll go as far as saying, you probably shouldn't even take an extreme truck on green lanes, as it just promotes a bad image and likely causes more ground damage than anything else.
There are P&P sites, now don't get me wrong. These can be loads of fun. But there is likely a limitation to just driving aimlessly around trying to get stuck. The novelty probably will ware off, as in the end, once you've been stuck in the same place time and time again, you'll probably just get a little bored with it.
To this end, I would advise not building a 4x4 with the sole purpose of P&P sites.
There are competitions. These aren't for everyone either. But they will generally test both the vehicle and the drive a lot more than a P&P site will. If you think there is a remote chance you'll want a go at this (and there should be, as it's great fun!!!). Then consider what attributes will be needed to make it a capable competition machine.
There are many types of competition, ranging from RTV trials through to Comp Safari speed events.
6. Along these lines, it's well worth spending some effort reading up and understanding how suspension works or why certain things work. It's very easy to spend a fortune on a pile of shiny parts, but only to find out that they don't really work well together or maybe not at all.
In fact it's amazing how many modded Land Rovers, especially Discovery's there are, that actually perform worse off road than they did when stock.
7. As an example, you've mentioned dislocation cones several times. Well my question is, 'why' do you want or feel you need dislocation cones? Do you understand what they actually are offering? And more importantly do you understand the limitations they also bring?
I'm not saying don't get them. I'm saying get them for the right reasons and knowing exactly what they are offering and what they might not be offering.
8. As for lifting a Disco, there is a link in my sig you might want to click and read, rather than me re-type it all here.
However the cliffnotes are. You probably want to lift the vehicle the minimal amount you can to achieve the suspension travel and wheel fitment you want.
Body lifts and body trimming are likely 'better' solutions, if actual off road performance and ability are what you are after, rather than jacking a vehicle high up in the air. But suspension is part of a package and should be considered with other components and intended use.
However as an example of what can be done easily. This is my old Disco, it's running 33.11.50R15 Simex's, they measure almost 34" tall.
And.... it's on 100% stock suspension. Stock spring, shocks the lot.
Stock suspension is actually a very good compromise for all round general use, as it'll work well off road and on road. Now I'm not claiming this was the ultimate setup, it certainly wasn't. But it was a good setup as it still drove and handled well on the road. But also flexed fairly well off road. Because it retained all the positive attributes of the standard setup and wasn't riding a mile high in the air on a super rigid HD suspension lift.
With a traction aid like TCS or some different axle diffs, it would have been extremely capable.
9. Do remember a good suspension system should allow plenty of up travel as well as down travel. So 'lifting' to fit bigger tyres only works if the suspension is never going to be compressed, as compressed suspension completely negates the lift.
10. I did watch the vid of the blue D2 you posted (running the same Simex tread as me
). It does look nice and Tonka toy like. The only thing to note is, we simply don't have terrain really like that all that often in the UK. Some parts might be rocky, but our Green Lanes really aren't like the American and Australian trails they go wheeling and 4x4'ing on. Remember Green Lanes are actually roads, i.e. ON road driving, not off.
To that extent, some of the most capable 4x4's on UK terrain look like this:
Worth noting is, as a rule they are not large lifted vehicles...
11. As for the suspension on your D2. I honestly think the best thing is for you to do some research and then pick or design a setup that will actually suit your needs and goals with the vehicle. But base your selection on an 'informed' opinion, by understanding how and why the different setups work and for what sort of use. Rather than just buying what some bloke on a forum told you to get
My own personal view would be, a 4" lift sounds excessive and will likely mostly result in a taller vehicle that is less stable on uneven ground. And you'll also likely hit lots of issues with on road driving too. And I suspect you may struggle to retain good suspension travel and a lift of that height.
ACE is awesome. I'd try and keep it, even more so on a lifted vehicle.
Air suspension can be good, don't dismiss it straight away.
Dislocating suspension system often look good in photos and for RTI ramps, but in practice probably try to solve a problem that doesn't exist and they do create other issues all of their own. My own preference would be for a retained system with good balanced suspension travel on both the front and rear axles.
