that swap is chock full of sacrifices, I believe you give up power steering, A/C possibly and any cornering for the nose heaviness it brings with it. I was in on a 383 swap in a 69 dart, fender well headers etc. with a friend of mine. it was his car. i don't recall it ending up being any faster than a well oiled and tuned small block. i suppose if you are drag racing in a straight line its worth it, on the street not so comfortable ( the nose heaviness)