The 4btswaps.com site is a good one that is a offshoot of the yahoo group. Which still exists but does not get much use, but some. You would have to do a SOA setup(Spring over axle). But boy you are talking about quite of work. It can be done. Like the 6bt in a S10 I saw.
Weight is a BIG problem as other people have talked about. A VW diesel TDI would be good and they can be hopped up. I know they make a 5cyl inline but not sure about a V6... But a car based engine would be better. The medium duty engines have things to over come.... 453 Detroit Engine is the same. Cat makes some engines. I have helped put a 3208 V8 Cat engine in a one ton truck, but it was almost a Steven King movie.5pd tranny and a 3sp brownlite aux tranny.. The better one was a Perkins Diesel in a one ton.
I was going to put a 350 olds diesel in a s10 but the Blazer deal did not work out. I have seen one in a Luv truck.... No need for comments on the olds engine. I know about all of them, including my 300k engine and my 400k mile engine. I just need to locate some oversize pistons and rings.. MY ARP head bolts and main bolts gave no problem. I worked on them when they were new.
Use what you can get or what you think will work... A 6.5 or 6.2 GM engines... They have been put on a Camaro and a Monti Carlo All have their problems the 6.2 and 6.5 run cast iron cranks but the Harmonic Balancer goes out and takes the crank with it. 100k it should be changed some say ever 70k
Sorry if this seem off topic.. But it was to show some options and problems... DO I HEAR a Duramax
ave
I do not have any experience with any of the Isuzu Diesels.