You know, I spent a nice amount of time finding a numbers matching 400 Car. Now after owning it for a few months my I have been slowly going away from completely stock. I did brakes, and suspension. So I have been buying pieces to do a GM LS3 Crate Engine swap. My point is do what you want to do with it. Body and paint your prob gonna be in it for 15k. I almost think If I had to do it over again I would have paid a decent amount less and bought a 326/350 car. But I will still have the original engine and trans stored.
Being you don't have the original motor put that 455 in there....