There is a balance between the cars performance and the engine power. A lighter car goes faster with the same HP engine than a heavier car. The lighter the car, the less power needed. With that said, the next issue to going fast is the limitation of your wallet.
Items that need to be addressed when you start pushing the Magnum design start with valve train stability and the head flow abilty's. You can have a cam custom ground to get around some of the heads short comings. Just remember that in the end, head flow is more the limiting factor than low compression. You can mill the heads for some extra compression but there is also a limitation there as well.
Now with the above said, I have seen box stock Magnum engines run with bolt on parts, ported iron heads and a cam run in the 11's. I do not know how streetable they were/are to you or the owner of the car. It's a personal thing anyway as to what you can live and deal with.
On the F.I. Issue, I'm not sure what you can do with the stock system, or computer. The versions I see mostly are carbed.
