Hy SimS, the balancer for the 454, and 400 small block are special items and have a weighted area to assist the weighted flywheel in externally balancing these engines. When the 454 first came out I worked in a speed shop, our new flywheel catalogues came out the next year, and they listed the same p/n for all the big block Chev engines. My boss sold a flywheel/clutch package to a rich kid, in about two weeks the kid and his dad were pounding on the counter telling us the parts we sold were crap cuz since they put them in the car vibrated all the time. It took awhile and a lot of shop time and money to figure out what was wrong, but my boss called the high perf parts guru at the local Chevy dealer, and he nailed the problem right away. Seems we weren't the only speed shop in town that this had happened to, and not the only city either, there were lawsuits flying around for years after that. And new pages for our flywheel catalogues with triple size print for the correct 454 flywheels were issued very shortly after this fiasco!
