Starter Questions

[502ms]

Hello - I am in the midst of (well, I will when I get home from work), pulling out the starter in my 72 C10 Stepper. It has the 350/TH400. My question is with so many different starter options out there (regarding flywheel and shimming, etc.), how do you know which flywheel you have with out pulling the tranny out? Is it stamped somewhere? Currently, my starter just kind of semi-turns and cuts out...sort of like a "hum". Battery is fully charged, and no dice. I have Sanderson shortie headers now to help with the proximity to heat issue that the long tube headers gave, but I think this starter has seen its last days.

My question is how do I know which one I need? 153 or 168? Ideally, I would like to pickup the starter, go home, remove the old one, install the new one, and be done with it. But I am not certain which flywheel I have.