ah, hmm, we have switched before without this problem. There are two different types of common Delco's. I have a Delco on my 7040 from a OEM neihoff and have switched tach - drilled the rear plate to accept the pickup off an 8000 series. There are also different pulleys with different offsets. However , and my memory ain't what it used to be, I think I used the same pulley off the NHF. I will do some checking this weekend.
