"....If you had a '54-'í56 block and you wanted to use an adapter with a later model trans, you'd need the 130 tooth flywheel from a 426. It's an eight bolt flywheel (with the asymmetrical bolt pattern) that'll bolt right up and work with the later model gear reduction starter used throughout the sixties and for the next 30+ years, HOWEVER, with your extended bellhousing you're pretty much limited to the 146 tooth flywheel as the ONLY option and the only starters that'll work are the stock 6 volt starters up to '55, the '56 12 volt starter or a PowerMaster starter.
If you find a 172 tooth flywheel, sell it to someone with a 392 because it won't work with any starter you can find on that block......"
I thought I'd throw this out as a for what it's worth thing (although it doesn't really pertain to the extended bellhousing as mentioned because of the starter issue).
According to the Wildcap site
".....Also the 426 Hemi flywheel has the correct bolt pattern but does not register on the flywheel correctly and can't be used....."
From my own experience, don't overlook or throw away the Poly flywheels (1957-1961) if you happen to come across one. Yes they are six bolts not eight like the HEMIs but they do bolt up to the Hemi Crank and register correctly. It is possible to drill and add the additional 2 studs if desired or run as is with only 6 bolts. Keep in mind that Chrysler only used the 8 bolt crank on the HEMIs and 6 bolts on everything else to include the 440s. Personally Iím not bothered running with only 6 studs in a mild street application.
The flywheel is too large (diameter) to use with the late model bellhousing/adaptor, but any machine shop can turn them down for the 130 tooth ring gear. The last one I had done cost $30 to turn down and have the ring gear installed.