My 69 400 is rebuilt to original specs. It's mostly original under the hood with some added ignition electronics. It runs perfect. Doesn't ping or overheat. Has just the right amount of power. The only drawback is that I have to mix 93 and 110. Notice how I didn't mention zero decking? It isn't necesary. It may very well be an improvement. But why change a good thing? If you build it as it was when new it'll run good. Make sure you feed it right and it will treat you right.