I think youll be fine, but as I always do get another opinion. My setup was done when I bougth the car. Just get as big as a cell as you can fit, 502 bbc suck gas. Check these guys out:
http://www.rickshotrodshop.com/musclecartanks.htm
I have a 12 gal in the trunk and might remounting under the car.
Good luck.