Cheap 318 performance mods.

Diy porting the heads is cheap. If by some chance you can get them flow tested, the flow numbers will help when selecting a cam.

Cleaning up any casting slag or imperfections in the new intake manifold and in the ports of the heads.

Timing recurve, you can get lighter springs for the distributor and then try and find the sweet spot for total advance.

Headers and dual exhaust(this may or may not be cheap)

That's very cheap power