The easiest way would be to find a rotten V8 Discovery 1 and use the whole engine, transmission, gearbox crossmember, front prop, front section of exhaust, etc.
The front half of the Discovery 1 chassis is virtually identical to the 90/110 chassis other than the engine mounts, ideally to put the V8 engine in the standard position, you would use the matching Discovery crossmember, which would move the transfer box a couple of inches further forwards, the same as a 300tdi.
The problem is that most Discovery 1's have dissolved, so could be hard to find, a Discovery II is probably more available these days. I'm not sure how they compare to the Discovery 1's mechanically, the chassis is definitely different and more rusty, but they do use a similar transfer box. I imagine the ancillaries will be the issue here.
Alternatively you can use a V8 conversion plate from a Series 2/3 conversion, which will mate to your existing gearbox, but puts the engine way back in the engine bay, in the same position as the current engine, which creates its own problems. With a V8 conversion plate, you may have to chop the passenger footwell and you will have to fabricate the front section of the exhaust.
