You should seriously consider doing a electric pump setup. The top rated mechanical pumps are in the ballpark of 80 GPH, IIRC, whereas I had a 280 GPH pump on my 347 car. (good for 800 Hp)
If you're doing nitrous, you need to do one of two things:
1 BIG pump (such as a Barry Grant 280 GPH)
Or 2 smaller pumps, one for nitrous, one for motor. (such as dual Holley Blue's)
Best setup for the tank is to sump it, requiring a $70 part welded onto the bottom of the tank. It can be a chore finding a shop to weld on a gas tank though, for obvious reasons. The other option is to get a fuel pump pickup from Summit ($70ish as well I believe, but this replaces the stock fuel pump with a pickup line-setup)
Look fowards to $500+ on a decent fuel setup, + more for the nitrous fuel setup.