Well I will attempt to help;
1. I can not imagine you would need a wiring harness without the F.I.
2. Not really sure but you may need them custome built(headers). A little expensive but you get what you pay for. Also until you can afford that you may be able to get away with the stock exhaust manifolds after all they were good for the 390 hp.
3. This is a tough one. I am sure there are other sights where people have made this sap so they would know better. Does it look like it will fit now?
4. One of 2 ways a 200 wet nitrous system or a forced induction(super or turbo). A cam swap headers and since you are changin the intake already you will get a lot more hp then stock, but I am not sure about 200hp.
Sounds like fun. It was something I wanted to do to my camaro but the ls swap including the engind and all associated parts costs more then keeping my big block rebuilding it and adding a supercharger. That ls stuff is expensive but worth it.