"An early S-10"- - - - -the first few of them had a 2.8 liter V6 with an oddball carburetor and a distributor with a vacuum advance. That one would be a nightmare to swap, as the bellhousing bolt pattern and a lot of other stuff won't be compatible with the running gear mated to the 250 I6. A 4.3 with a carburetor would be a lot simpler. If the throttle body fuel injection is involved, the electronics are going to get pretty hairy because of all the sensors needed, the computer, and the fuel tank mounted high pressure fuel pump. Mercruiser made a 4 barrel intake for a 4.3 that ran a Quadrajet, and a non-computerized HEI distributor with only centrifugal advance, I believe.
Jerry
