Do you already own the V6 'stang? SN95? If so, you could swap in a carb'd Windsor. That would be the cheapest route.
Basically, you'd need:
1. Upgraded diff. Swap out the 7.5" for an 8.8" with 31-spline axles and gear (3.73's, 3.55's, around there).
2. Suspension suspension suspension. Did I mention suspension? You'll need springs, bushings, shocks....etc. Lots of power is useless if you can't get it to hook.
3. Big 'ol Windsor. Find an early block (69-era) if you want something REALLY strong 351W. Get a stroker kit for it (408 is a common one). If this part confuses you, you could get in touch with Woody from fordstrokers.com or Jay Allen from camshaftinnovations.com (both hang out on SBFTech) and they would work together to build you a mill easily capable of your goal.
4. Transmission. Built C4 or C6 is probably the easiest route. Though an AOD can be built as well and gives you the luxury of overdrive. If you want the manual route a TKO600 should be able to handle things. Don't forget the clutch!
5. Induction. Work with the guys I mentioned earlier if you are puzzled about this part. Topping it with a Vic. Jr. and a big Holley from ProSystems is probably the "best" route to go here. You'll need a cowl hood to clear that intake/carb combo however. The Windsor is pretty tall.
Cammed by Jay, as long as you specify you want good street manners, it will run around town sounding almost like a stock V8. Until you get on the loud pedal and holy [censored]! A buddy's 302 sounds VERY mild, yet has run bottom 12's on street tires un-tuned, far from optimal at 114Mph. We've got a Vic Jr. and an HP Holley to put on it, set the timing curve, then wideband it and she should be deep 11's on a tire. That's a stock compression 302's with some "out of the box" trickflow heads, street-friendly cam...etc. The car is very light however.