I am shopping for a new starter to throw on my 350 sb chevelle, but I dont know what kind I should get. I have noticed that the main difference in high-torque starters is in the number of teeth...153 & 168. Does the number of teeth make a difference on the starter, or are they meant to be application specific? If someone could please explain this to me I would greatly appreciate it, thanks!  

Application specific based on flywheel/flexplate diameter. General quick way to tell is that 153 tooth 'wheel uses a starter with straight mounting bolt pattern. The 168 (which is also used by the big block) uses a stagered mounting bolt pattern.

Bogie