About 10 years ago, I wanted a larger capacity E-Body tank for my 1970 'Cuda. The stock tank has a pretty small capacity in relation to a big block Mopar's thirst. I worked with Hector at Rick's tanks and had him add extra width and a deeper stepped bottom to the stock dimensions. It bolts right into the stock location still, but holds more fuel. A few years back, I added a removable top plate and a couple Holley Hydramats with -10 pick-ups that feed an externally mounted, 2 speed Fuel Labs fuel pump.

I would never go back to a stock tank for many of the reasons you are attempting to resolve with your tank swap. Perhaps, you can give Hector at Rick's Tanks a call and see what might be the best path for you?