[John Rogers]

There seems to only be one voltage regulator now, the solid state one which is for busses and 914s, etc. There are two alts that will fit, the 55 that you have and a big one (90) that is from camper vans and 1976 914s that had a/c installed. The connectors are swapped on the big one and require a different harness or redoing the connectors at the relay board (swap DF and D+) or you'll get 18 volts at the batt, NOT good. I just went through this problem a month ago and I fell the best thing is to get a new regulator, rebuilt Bosch alt, a sealed batt and new 3 ga wires which will be good for several years. Good luck.