One of my cores (from 1990) was on the car when my dad passed away. It worked fine but was a 2 pulley. The charge indicator bounced a lot at idle.
I replaced it with a single pulley ( the one the last failed) the charge indicator did not bounce at idle.
Difference... 2 groove was 3", 1 groove was 2.7", parts book calls for 2.5". It would probably charge with the headlights and brakes on at idle with a 2.5".
The square back I bought for the time being, bounces at idle... 3" single groove pulley.
So size does matter and sometimes smaller IS better!
