My 2 cents. If I was doing it all over again I would build a stroked 400 . 400's are often a better, stronger block than the later 455 blocks. A new stroker kit would give you almost the same displacement as a 455 with all new, stronger than stock, internals. there are some nice kits out there. once you know your going to rebuild, pull your engine and strip it and get your block tanked, crack checked, and tested to see if it is a good candidate for rebuilding. the jim hand book is a great reference to teach you the basics so you know what your machinist is talking about.
then just open your wallet and watch the money fly out...