Programmer won't work on an OBD1 engine. For that matter they don't do anything (powerwise) for the OBD2 Dodges.

Being that it is OBD1 however, you can go a long ways hot-rodding it if you do open it up. They are a bit more tolerant of mild cam changes, upping the compression and porting the heads (yours should have J's and can accept 2.02 valves) than OBD2 stuff.

Without opening anything up: a true dual exhaust would be step one, electric fan, and that's about it. If you have some fabricating skills you can always find a 5.7 Hemi airbox that some Goof threw off his new truck for a "cold air kit" and make it fit your van. Putting it all together should get you about 20hp, about 20-30 ft-lbs torque, and about 1 or 2 mpg better.

From my understanding this engine you have has alot of great stuff already in it such as a factory roller cam and the good heads.