Flywheel size??

[igasem]

I'm changing my automatic trans to a Tremec T56 and in the process I need to buy a flywheel. Anyone know the difference between 153 teeth and 168 teeth besides the obvious "15". I don't know if there are different styles of bell housings or exactly what determines this. Does the starter have to have a gear to match or does one size fit all?

 

[jlcustomz]

Generally, as far as I know, Ive seen 153 tooth on a 305 & 168 tooth on a 350 ist gen sbc. The starter mounting holes are different to compemsate.

Ps, like my 99't-56, no slush box here.