I race in NHRA division 7 for many years, they decided back in the early 1980s that their Pro Tree for both Super Pro and Pro bracket races would use a four tenths Pro Tree, not the standard .500 tree we see now at the races shruggy
All the other divisions use the .500 Pro Tree confused

Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)