Combines new or old style rotorIJ

They offered two styles of rotor in 1990, a specialty rotor, and a regular rotor. The specialty rotor had rasp bars all over in "random" locations. The bars are about as big as your fist. A regular rotor has three rows of rasp bars running front to rear. The front section of the bars are in a helical pattern, and the rears are straight in line. These bars are about 10 to 12 inches long.

i'm new to rotors ran a white 7300 for 24 years, is there a big difference between conventional and specialtyIJ are they upgradable if one is beter than the otherIJ

Specialty rotors are more agressive, which makes them better in tough viney beans. Regular rotors tend to do better in white corn, popcorn, and food grade corns. The specialty rotors shell corn awfully good, I think they're better as a whole.