I have 168 and 139 tooth flywheels for GMCS; both are the same diameter. When using a 168 with one of the "little" starters the Chev V8 is correct for the drive gear.
If you want to use one on the 139 tooth, the original Nissan starter drive gear will be correct. I had 2 adapters made 25 years ago for the 2 hole starter mount on stock bell housings using the "little" starters and RB starters in Long Beach told me the stock gear was correct. I used them for years prior to purchasing on of Buffalo's plates.......Good Luck

216.158 MPH 12-Port 302 GMC on 70% 171.0 MPH 302 stock head on gasoline 7 years later