I agree.
Some might be attracted to the car as is because of the recent paint work, interior work, etc + the economy of the /6.
Offer it as is, and a decent deal on the v8 stuff, so you get a reasonable price, and both go, if not, keep the small block lying around for something else.
I regularly drive my Dart, because I can afford the gas for the /6, were a V8 car, would get driven less, and enjoyed less.