Stock is cheap, stick with the GM 6 if money is the major factor.
To do a nice job on any sort of Diesel conversion it takes time and money, usually lots more than you can imagine from the start. In my experience the cost of the engine is a small part of the whole project/cost because updating an old truck to make good and safe use of that better engine takes so much more.
Not to say you can't plop any sort of diesel engine that fits in there on the cheap... But if that's the results you are after you'll probably be better off leaving the truck stock, it'll look better, be worth more, and you will have saved time and money.
A 4BT Cummins should be a very straightforward swap but not eat up with HP. It'd be great for going to shows and saving on fuel to get there, probably never save what the conversion cost..
Grigg
