a 194 head also works with the 250, and will increase the compression. GM started those integral intakes in '79 or '80 I belive. For that engine, Clifford research is probably the best, but it will cost. Speedway motors sells basic intake and headders.

I would run a properly sized Turbo. a Holset HX 35 would be just about right and they came in some diesel pickups, but you have to get the non variable vane version