heads
What are you goals with the engine? It should be the standard intake bolt pattern so any intake with a square or spread bore for a SBC will work. That era heads are quite restrictive, If you want to make more more power I'd look for a set of the 96 and later vortec heads, found on the trucks and suv's, in the junk yard or online and then you'll need a vortec carb intake but still everything will bolt up.
Well depends what your goals with the engine are. if you just want it to run then you can change it over and rock and roll. If you want to make power then I'd look into a change of heads if it were me. I think that 1990 engine is in the low 200ish range hp wise stock.
No problem, might be worth it to ditch all the electronics and stick a regular distributor in while you're at it, and eliminate the computer controlled timing. Any HEI or ready to run will work, or get a billet distributor and an ignition box.





