I'm looking at starters and wondering how many teeth are in my 1972 flywheel?

Thanks.

Look at your origional starter. If the mounting bolts are strait across from eachother the flywheel is a 153 tooth. If they are staggered it is a 168 tooth flywheel.

My SB had the bolts in line with each other and I had a 168 tooth. I know cuz I counted them.

Looks like some starts go either way. How tough is the change out? Can you count the teeth w/o a tear-down?

You can count them. Remove the dust cover & pick a tooth to start with & put a mark on it (paint marker etc.) you will have to roll the engine over to get to them all.
Another thing is the 168 tooth auto flexplates (did'nt say if it was an auto or manual) have a dual bolt pattern for the large & small pattern converters. The 153 only has the small pattern. So if there is a set of converter mounting holes that are not being used it should be a 168.
If it is a manual I guess you will have to count. Hope this helps.