Speedometer Gears vs. Tail Shaft

I have a PMAC/Century Automotive transmission. Very happy with its' performance. However, had a little trouble getting the speedometer to read correctly. Had to use green gears (10 tooth drive & 29 tooth driven) to get 67.5 MPH at 2000 RPM. Study of three other GN transmissions revealed that an orange 11 tooth drive gear and a blue 30 tooth driven gear should have been what was needed.

Is it possible that the tail shaft in my transmission is a little different? Just courious to see if GM made different tail shafts for the 200-4R.

Also, speedometer reads correctly but Scanmaster speed is about 10 MPH less than actual. Does this matter?
You are ok...

Ratio is close .3444444 vs .3666666 that would matter miniscule.
As for the scanmaster, that is odd as the vss is reading the same ratio. hrmmm .Maybe the fact that the driven gear is still sped up due to the 29 tooth count that maybe doing it. Why the speedo is on and scanmaster is low is odd tho.