If the handling is sorted (takes more than just coilovers to make a capri handle), brakes are good, you got bucket seats to keep your ass in when cornering, a decent LSD, and it really is engine next, then usually it's decent exhaust inc manifold, decent cam, then twin 45s, decent light flywheel etc.
If it needs building, most go 2.1 with V6 pistons and a bore, then up the compression at the same time, etc etc. They have massive ports so never need a huge amount of headwork until going crazy.
If you was lucky you might find all the bits to do a V6 swap for a grand, but most V6s are fucked these days, and unless you could get all the bits to convert to injection and do a 24V Cosworth swap, which is unlikely for that money, you'd get the same sort of power (prob more) with better revving from the Pinto.