Big block,292 I6,Cummins. All would be big torque low rpm which is what that truck is already set up for. I'd be in the 454 or 292 camp. A turbo on the 292 would be awesome. Some other slightly more difficult swaps would be Big Caddy,Olds,Pontiac,Buick. The Olds ,BBC,and 292.
could be a bolt in...