That is the truth, everybody I know gave up because of cost, with only one or 2 due to health reasons, if I had a steady stream of cheap smokes, I would probably still be on them
If you are, and its just slow, could you not try jumping it straight on the starter motor? Both pos and neg, would rule out whether it is starter or not
Black smoke is overfueling, white smoke from cold start will just be condensation, you can get white smoke from injector pump timing being out, but you would constantly have it , it wouldn't clear
There is a company over here that does a conversion to a later range rover engine, 3L I think, can't remember the name, symtek maybe, but its pricey
Edit- http://www.bodylogicuk.com/90265/info.php?p=11&cat=327170