I build my cars to drive them like they were intended, thrashed on! When I restore a numbers matching car like my 70 GTX, I keep the original engine and trans in the shop and build another so I wont have to worry about damage. I gaurantee, if you have to sell it, having the car with a built engine in it and including the original will not hurt its resale. It also depends on how fast you want to go, if a 13 second ride is good enough, you can get there with a lightly modified 383, if you want 11's or better, go with the 440. My .02 Lee.