It takes some pretty expensive valve gear modifications (rollerized replacements for the original stamped steel rocker arms and aluminum pivots) before the top end is reliable at any kind of speed. Also, the only way of adjusting valve lifter running depth is by grinding valve stems or installing different-length pushrods after a valve job. The 455 pistons are dish-top only, and there's no flattops available without going to high-dollar custom pistons. However, a 455 Pontiac piston is the same in every dimension except bore. Bore a 455 Olds .025" oversize, and use a 30 over 455 Pontiac flattop piston to get more compression. The wrist pin size and compression distance are identical, and the weight is within just a few grams of the Olds.
Given a choice, I'd rather have a 500 Caddy over the Olds 455. more cubic inches, less weight, and less-expensive hotrod parts for that one. Joe Mondello is the go-fast guru for Olds engines, and he's an arrogant jerk who thinks his parts are gold-plated. Don't bother calling his "tech advice" line unless you're ready to buy only the parts he sells!
Jerry
