I would just use the gasket. Make sure you tighten the manifolds up evenly or you could get an air leak (inlet manifold) or exhaust blow.

Timing chain rattling. Fairly easy to sort out if you just change the tensioner.

Carb lapping: http://www.lrfaq.org/Series/FAQ.S.carb.zenith.fix.html

What carb do you have? If you have a Zenith they are know for body warping, causing your symptoms. There are threads on here on how to flat one back. Some Zenith copy carbs aren't very good either, even when new.

Rover v8 firing order. 1,8,4,3,6,5,7,2

I don't own a V8 anymore but iirc genuine dizzy caps are blue try a new one of those too.

Start it up in the dark, lift the bonnet and look for arcing/earthing from the ignition system, replace any duff parts. Check your dizzy cap, again, some pattern parts are cr@p.

Try a quality rotor arm. Some of the pattern ones arm very poor. Is it points or electronic dizzy? If its electronic it could be the amplifier (usually a little black box on the side of the dizzy - sometimes remotely fitted near the coil on earlier versions). How are your plug leads...

I like the sound of your ( or someone elses) bodge thread make sure there are plenty of piccies!

Result! Glad you got it sorted

Does it start OK when its hot? Maybe all of your glow plugs have packed in. As they are wired in parallel they will still work even with 3 u/s. Maybe your last one has expired or the wiring has been damaged/detached.

I had an ex military late 2a once, again fitted with a series 3 grill. Like you I baulked at the price of a 'maltese' grill so I made my own from 1" weldmesh. Cost £0. Picture is a little small and dark sorry

"Hand me the black cap, will you, I'll be needing that" - YouTube

The Lucas and Ducellier diizzies are interchangable. The ducellier ones were standard fitment to 2.3 and 2.5 engines and were an 'upgrade' to older units. Which is better? I don't think there is any noticeable difference, other forum users may be able to offer pros and cons of each design...

Did you manage to decode your VIN?

If you have a 17. Digit VIN then you can decode it here https://twinwoods4x4.co.uk/how-to-decode-your-land-rover-vin-vehicle-identification-number/

awe c'mon... LANDROVER HISTORIC VEHICLE | eBay

Loads on here: Has anyone dealt with Image 4x4 before? | Page 2 | LandyZone - Land Rover Forum

I've never had dealing with him or any of his companies but his name is familiar, have you tried googling him or searching on here?

The charge light wire from the alternator to the bulb might be earthing out somewhere, possibly where it goes through the bulkhead (chaffing) or if its too close to something hot the insulation might have melted through.