the 2.8 manual won't last and you will have a hard time bolting it up to a sbc as there are no factory bellhousings. its the T5 trany, it is weak, i blew one up behind a 2.5 2wd.
the 4.3 MAY last, it is a NV3500 which was found behind some 88 and newer 1/2 tons. the problem is you will only beable to run a s10 transfer case as the adapter is a 5 bolt pattern instead of the 6 bolt found with the np208 or np241. with the s10 transfer case, its driverside drop only and its not that strong.
its best to use full size parts in a full size truck.