mi5.0

I purchased a 92 5.0 hatch with 90k on car, I want to build it close to show room. But my question is starting with the engine, I'm looking to spend $3k to $5k and target hp is 400-400+hp. What would be a good route to go. I want to retain the EFI(I understand I can get bigger injectors, etc), should I be able to get that much hp on stock crank, pistons, block. Or will I need toimprove some of the stock rotating parts, should I just buy a high performance long block, I need some expert input. One other question, will the ECU have to be retuned or can I purchase a programmer and set it up for the changes I make for the best perfomance.