I'd say:

1: Yes the injectors will cope
2: I think you may want to think about an uprated clutch.
3: The heads are fine on this engine, I think you'd spend alot of money for very little gain on the ports/valves.

Dump the Miltek bits for Piper though.

I'm not sure if the Cosworth inlet manifold actually does much for the money if you don't spend on a better throttle body set up (someone will advise)