Hi. Do you mean the Halman Special which was based on the Irvine casting, with a special collar at the front to make a six-point mounting, or Hallman's latest, built on his own casting?
If the former, I suspect a normale p/c would fit. If the latter, I think only a limited number of motors were made, all with speed timing. I don't know if a std. Irvine p/c would fit.
I do have one of the former, but I won't be dissembling it to check the bearing. I will ask next time I see the man.
Wonderful motors.