[special-K]

The last 6.2s and first 6.5s share the same block casting. They are the same engine except bore. You can turbo a 6.2 with 6.5 parts or go to naturally aspired on a 6.5TD with 6.2 (or 6.5NA) parts. There were 6.5NAs offered for a short while,92+.

I mentioned the Isuzu diesel because I know of a conversion done in a square body several years ago. There was talk about using 4BTs,which are not made by GM and with the Duramax being the result of a GM/Isuzu partnership I don't see that it's that far off. Putting any diesel in a 67-72 is to gain some portion of benefit of economy,longativity,and/or power and a step away from keeping it original. We keep these trucks running with foreign made parts,even sold by GM,so...it's just a matter of where you want to draw the line.