Originally Posted By ct440rod
The long one that goes into block is 3/8. The one that goes into alternator is more like 5/16 but a 5/16 fine or course nut does not thread on it. Hard to believe it was metric in 70 . .


no metric threads used in 1970. possibly, over time, someone stripped or tore out, the original threads and re-tapped to metric in order to save the alternator. if you absolutely need to save it, drill and tap the offending hole for a helicoil.
beer