200Tdi 90 on standard suspension and standard 235/70 16 all terrains should do all the lanes in the UK.
What you're talking about is creating a bespoke off road vehicle, one that would have potential far beyond a muddy dirt track.
Everything beyond standard is a compromise, from suspension to tyres, even the wheel rims need a bit of thought once you start to modify.
Modifications come with costs and effects which in turn lead to bigger costs and before you know it, MasterCard has you by the short and curlies for £20,000.(maybe more but i know I could easily blow £20,000 on my D1 without it changing greatly from it's current look)
Sure, things like ATB diff's or even electric/air locking diff's are nice, but far from essential.
Big knobbly tyres look fab and have the desired effect of throwing mud all over your truck to show folks you use it off road, but they tear up the lanes you drive much more than modest A/T tyres.
Roll cages can certainly save your life in the event of a roll over and will give your truck a mean an purposeful look whilst giving you somewhere to hang other non essential accessories, but you'll pay the price in fuel and vehicle weight when venturing off road.
Everything has a cost to benefit ratio, I'm not just talking about £££££ but the big picture.
Few examples.
Big suspension lift, effect is raising chassis above the axles, cost is to the detriment of your prop shaft UJs and output bearings in your transfer case, your center of gravity is raised and handling characteristics altered by the rotation of the axle, brake lines all need extended too, all of which now cost more money and time to put right, all doable of course but at extra expense.
What about those big knobbly tyres? Well they will lift the diff higher up off the ground and new aggressive tread will claw through sloppy mud, but they come at a cost too, the bigger the radius of the tyre, the further away from the swivel housing it will need to be in order to keep turning circles less than an 8X4 tipper truck as they will now be fouling the chassis & suspension on steering locks, you'll then have to radically alter all 4 wheel arches as being so far out means on articulation the tyre can no longer tuck up inside the arch and sticking outside the body means you'll need spats/arch extensions to keep them covered, but how are you getting them away from your swivel housings? Spacers? Or offset wheel rims? Costs? Then you have to think next about the longevity of your wheel bearings being put under so much more strain than designed to cope with, what about the altered gearing from the increased rolling radius, potentially want you to alter the ring and pinion ratios in both diff's to bring it back to usable gear ranges, if you do that then you'll want to upgrade your diff centers to either lockers or at the very least stronger 4 pin units.
Just a couple of things to think about, but ask yourself how far you're prepared to go before jumping in feet first.
