The Mustang aftermarket is huge (for both suspension and engine components).
for the 5.0 components, the 4.6 is coming along but no where near what the old 302's had available to them.
Steeda, Griggs are some good companies for handling components.

For good data you can check out www.hardcore50.com, very knowledgable people over there.
Wish I could help you with the numbers for the mods your seeking on the 4.6, not too familiar with what best works for them...
I'd assume that for what you're looking, and how aggressive of a cam profile you're looking how, worked the heads are, size of throttle body, etc you could probably expect a 70-100hp increase with what you're asking.. again, this is a best guess.