Aftermarket gas tank?
You mean a square gas tank. Not with the area cut into for the spare tire?
Take measurements and compare with other tanks. Food for thought... E body Challengers also fuel up on the drivers side. Holds more fuel than a E-Cuda. Why I don't know but that's what the books say.
I'd like to know if there is a fuel cell that has the ability to install the fuel neck where I want it.