those motors are actually cheap for what you get....as I remember (when they were available) you could get one from pan to carb somewhere around 8K.
I sold a K to a builder in Florida doing just such a build. He had the yellow Dart....ground hugger AND show casing their aluminum Dana 60 they are producing, at the Nats last year. I have since seen the car in one of the Mopar magazines last fall.