They're not only different sizes, but normally different imbalances as well. Our cars normally use the 157 while older cars and mod-motor cars use the 164 IIRC.
like i need a nuetral balance flywheel, i already have a ram 164 tooth flywheel, and its neutral balance, can i use this with a 302? with the right starter for it? is going with a tremec 5 spd and ram diaphram clutch. now the diff in size im pretty sure the 164 is 11" and the 157 is 10 1/2. now if i use the 164 do i have to get a 11" clutch? also whast the diff in performance beween the 11'' clutch and the 10 1/2?
The blockplate that locates the starter is different with the different flywheels or flexplates. The blockplate, bellhousing and flexplate have to match, and all can be found for both sizes for early or late balance. Neutral balance would be a bit harder, but is available as a race part from lots of places.