I am literally getting ready to start this conversation in a week or two. We will hopefully be picking up a 85 military blazer next week. I decided to do a 6.2 conversation. From my research, as previously stated, all you really have to do is use big block mounts and your good. After tearing apart my 71, i found it already had a unused return line so you should be good there. Im planning on mating it with a manual 5 speed. the military trucks were 4wd with 3.08 gears, turbo 400 and the 6.2. they got around 20 on the highway. i figure with a od and a manual, i can get 25 solid. Plus as stated, they are cheap to get. Problem with the cummins is that they cost alot and, at least in my area, finding those exact bread trucks is hard. 6.2 is cheap, efficient and easy. Just my 2 cents. Upfront im looking at $2,000 for the swap but thats assuming i dont do anything with remains of the blazer.
Sorry for the long explanation but i tried to do my research and i decided on the 6.2.
http://67-72chevytrucks.com/vboard/s...d.php?t=469045
A thread i started a couple weeks ago.