http://www.dieselplace.com/forum/forumdisplay.php?f=20
Basically they are a 305 in power.
Unless the truck is being driven every day and can be shown to be running great, expect to put $600 in new parts (glows, fuel filter, injectors, and pump). These motors do not like to sit.
I bought mine 3 years ago, wish I had bought a gasser instead, the parts bill has been 4x the fuel cost savings, and the truck has only been on the road 25% of the time.
So far water pump, injector pump, injectors, injector lines, intake and gaskets, 3 fuel filters, fuel lines, CDR, glow plug override, crank pulley, braks 'cause it sat over winter while I chased down parts, etc. Next is another set of injectors and crank pulley (hint - the factory pulley is over $300!).
23mph in a fully optioned 1/2 ton with air. When it runs.