I have no experience building a stroker, but when I had my fox body stangs, I lurked a lot of 5.0 forums. What I saw was that most people would either do a HCI kit for the stock 302 (heads, cam, intake manifold), or would go stroker. A friend of mine has a 331 stroker that is supercharged in his GT fox body. He took me for a ride in it when it was just a supercharged 302 with HCI, and that thing was just silly! I can't imagine what it is like now.
You have a 94-95 5.0 Stang if I remember correctly, right? For me, if I was in your position, I would be deciding between going with a 347 stroker, or supercharging what you have. It all depends on how much $$$ you want to spend, going fast is NOT cheap, especially if you want it to be reliable, and not have to worry about anything breaking when you go out and beat on it. 400 RWHP will be a lot of power in that SN95!
This is all good bolt-on info Dirty, and these parts are relatively inexpensive as well. GT40 heads and an explorer intake (can get at a junkyard and clean them up), cam, and you'll have a fun little 302. Trickflow makes a REALLY nice HCI combo if you don't mind spending a bit more, that gets most guys to around the 300 RWHP mark, give or take. But if you want 400 RWHP, gonna need a stroker and or a supercharger. And 3.55's (Or 3.73's, which a lot of guys go for) is a really nice upgrade as well.
That said, even 300 RWHP in these cars will be a LOT of fun, you'll have issues getting that power down to the pavement. Like I said up above, it all depends what you want out of the car. A street car that could be daily'd that is a blast to drive (300 RWHP), or something that is more built, putting down more HP, that might not be as practical, and will be a lot more expensive both to build, and maintain.