Factory 72 Swinger

Your chances of "trading up" to an E Body that is worth anything is slim to none. Just go over to the E Body forum classified section and look at what those Cudas and Challengers are bringing in in the roughest shape you can find. Those cars are bringing stupid money and need TONS of money to even turn them back into something that even resembles a car.
Everyone else has said it, but it bears repeating. The car you have right now is a VERY sweet starting point of a project, one you can drive and work on at the same time. The parts for A Bodies aren't nearly as expensive as they are for E Bodies. This is a car that, if you part with it now, you'll be kicking yourself for later on down the road.
Nobody can force you to keep the car obviously. It's your choice, but, for lack of more politically correct temrinology, you'd be a bonehead to dump this car or trade it for an E Body that will need literally tens of thousands of dollars to bring back to the condition this car is already in.