The 2.5 Turbo D is useless, blows turbos quite regularly.
The 200/300 TDi is pretty tough - farmers here use them 365/24 sometimes for everything - as a car, animal carrier, trailer puller and even as replacement farm machinery. The 2.5 TDI used to power the 110 as well so its up to the job of replacing the 4.0 V8.
But if you can get parts for GM or other Diesels more easily they could be decent alternatives as long as they aren't too heavy.
A "chipped" 1.9 TDI will make 250-300 lb/ft and use far less fuel than a petrol V8.