That's the same route I took starting a couple years ago. I swapped in a 440 and 4 speed, and while the engine bay was empty had that painted. The motor and everything was done for about a year before I took the car back in and had the body work and paint done. There really is no correct way to do it (any way is good as long as the end result is what you want), but the nice thing about doing it this way is it spreads out the cost.