I tried to post this earlier but the forum is still dropping out for me.
The best route will be to get the 255 intank for now, then later you can upgrade with a surge tank and fpr, if you get to the point of making a lot more power.
Get rid of the idea that you're going to use a 460 on a stock reg. A drop in reg is all of $300 and is needed for the fuel system to work properly. Just because you can get away with it for a while doesn't mean you should. If you insist on a 460 intank then you need a reg too.
Be prepared to spend some money though, there is nothing cheap about building a properly done, reliable, high hp falcon. Also don't get caught up on numbers, 350rwkw is fast as hell on the street, never-mind going 400+.
Anyhow there's my 2 cents.