I have my dampener from the 496 here on my desk as I need to figure out what hub for an A fuel crank. The center is the 916661L which measures 1.190 from the face that interfaces with the crank / lower gear. The motor has the Jesel belt drive. I do not know if there was a spacer involved as far as spacing out from the crank. I do know the dampener interfered with the Indy cast cover when I tried to use it on the 540. A spacer probably would have cured that but it would have had to be thicker than the oil slinger that isn't there.

BTW, since I am going to replace the hub you can have this one for $50 if you need it.

http://www.atiracing.com/products/dampers/charts/damchrysler.htm