Don't be so quick to get rid of the little 'ol 350! Here's a pic of one of my favorite "sleeper" looks. It's also a 2dr post car like yours. Most people don't realize the post cars are lighter than the hardtops.
Looks like a great starting point to me. Alot better than the 72 i picked up today. Granted i wanted something that needed work so i can practice and learn from since its my first project car.
I bet you could score a nice set of Buick rally wheels and some new T/A rubber with spare change left over for what those 22" could sell for. :beer Are there any modifications to the suspension?