I have been running a 6.2 for the last 5 years in a 110. I started off with a LT95 box but took it out after a few months as you could go anywhere in top gear. I am now running a V8 spec R380 for the last 4 1/2 years with no problems whatsoever with it (touch wood). It was a rebuilt Ashcroft unit. Axles are bog standard and I have only broken one front halfshaft trying to climb an impossible hill.
The engine I originally bought from Coastal Engineering but I have also dealt with Samauri and I can safely say I would never again deal with any of them (Coastal is long since defunct, I believe). The way I was treated and the quality of the rebuilds left something to be desired. In the 60,000 miles the engine lasted I replaced one head gasket at 1400 miles, 2 heads at 14000 miles, a couple of sets of heater plugs, about three sets of starter bushes & solenoids, a new starter and the list goes on. This engine finally died at the end of January when three main bearing webs on the block cracked. With a lot of soul searching as to whether I would stay with one or go the TDI route I finally decided to stay with the GM. However I had been following a website in the states about these engines for a few years, over which time I got a feeling for which people to deal with. I elected to go with a company called "The Diesel Depot" in Georgia but ended up waiting over three months to get it built & shipped over. However the wait was worth it as the quality of the rebuild is far superior. Actually I found out in the process that Maddison 4X4 use this company to supply engines for the Ibex's they build so maybe you could give them a call.
I think with the situation you are now in I wouldn't even consider transplanting a GM into it as the amount of re-engineering involved to do the job properly is massive compared to putting in a TDI unit. For example I am running twin snorkels through twin tractor air cleaners. Exhaust is a twin 3" setup with 4 silencers and crossover pipe, all custom made. You then have to think about suspension mods as the unit is a good deal heavier. I assume then you would also have problems with conversion plates, flywheel, engine mounts, ancillary mounts, cooling etc. The list just goes on. Then at the end of all that you have the biggest hurdle of the lot...........................INSURANCE. You mention 6.2 litres and most insurance companies will run a mile.
I think at the end of the day a TDI would be your best bet. Its a land rover engine, its fits easily and it suits the vehicle. If I were starting from basics again like you it is what I would do. I fitted another one because I had all the conversion work done and the insurance sorted out. Oh, and that lovely V8 sound on full load. Fyi MPG in a 110 weighing 2.6t is 20-21 empty and 17-18 when towing. If I can be of any more help just ask, as I had to learn a lot the hard way.
