Original 3310 750's have 72 primaries and the secondary plate is equal to 75 or 76 jets if you convert.
As for the CFM, the original 3310 was rated at 780. Subsequent versions were 750 because of changes to the boosters. I believe the newer ones had a "bridge" across the booster opening while the originals didn't. It apparently hurt airflow but helped the vacuum signal to pull the fuel through making more responsive.