The Toyota and Nissan diesels you are referring to are real tough to come by, being out of production so long hardly any are left and usually real (comparitively) expensive when you do find them.
But not to dismiss your idea (cause I think it's a good one), try finding a 220D or 240D Mercedes with a four or five speed trans (they also came with a 4spd auto)
You can find rusted out cars complete for less than the cost of etheri of the other diesels,they have more power and Mercedes can get any darn part.
You would need to use a sammy case, make all the mounts and a couple of driveshafts but I think you would end up with a real good ride!
There are also diesel Chevettes, Peugots, and a couple of others...can't remember names right now.
Zag