That is quite beyond me...
But I know for sure that it is a regular grain film (not T-grain).
Going through Wiki, I found this:
Type 51, ISO 640 print, ISO 80 negative, black and white (very high contrast print, reusable negative)
So, processing for an ISO 80 with regular film should be about the same...
But since the film is somewhat expired, I wouldn't be scared to overdevelop a bit...
(If I just had that old Kodak paper computer for film sensitivity and processing type...)