Sounds like you want a gas tank to match whatever dual exhausts you already have?

I have used two different styles of dual exhaust systems with a 235/261 and the stock fuel tank (47-55 panel body trucks).

Patrick's and Chevs of the 40s should have a dual exhaust system for use with a stock tank. Jim Carter used to have a dual-exhaust system that worked (but it did not fit well with a 4-speed transmission).