Cheapest Mods for my 96' GT

[T-Bone]

Thank you all very much for the advice and suggestions. I am considering all of them and have a list of things I'm planning to do to my 4.6L. They include the following items(not in any specific order, but closer to tax return time hopefully):
Pro 5.0 3.73:1(I guess this is the best since it seems to be the most popular ratio)
March Underdrive Pulleys
K&N Air Filter
Flowmaster 2 1/2" 3 Chamber exhaust
Bassani X-Pipes
Pro 5.0 shifter
70mm-80mm Throttle body?(not sure if bigger is better)
Motorsport Headers

I think that about covers it. If I've left something out let me know. Or if any of these parts are not recommended or are incompatible.
That should keep me busy for a while. Maybe later I'll try NOS. Seems awful cheap. Is there a downfall to this. Any experiences you could tell me about NOS(good or bad)? Is it legal in a street car? Is it bad for your engine?

Thanks again
T-Bone