My brother has one in a 455 olds and another going in a 350. You can't hear the gear drive on the 455 because of the 3.5" exhaust. They do take a little time to install them.

On a related note has anyone ever ran a belt and and a gear drive back to back? My machinist had a single idler gear drive on an injected 355 sbc and tried a jessel belt drive for the heck of it. The belt drive slowed the cars 60' time and as soon as he put the gear drive back in it returned to normal. He came to the conclusion that the belt was stretching a little when the car was taking off and in turn it was throwing the timing off enough to kill a little power. This particular engine is in a flyweight opel gt and revs to 8-9k very easily.