Don't trust my memory on the charging thing I had a couple of strokes and can't quite remember if they don't charge at all at idle or if they just need to be revved to around 1200 rpms to excite/activate them and then they will. Your car if originally a 350 2 bbl had a externally regulated alternator but with a 400 ram air in the same year they were using the solid state internally regulated alternator that they started using in all cars in 71 and all the way into more modern times. it uses a 3 wire setup, a battery wire that goes to a stud lug on the outside back of the alt. housing and 2 wires in a shared flat plug on the side. 1 for the warning lamp system in the dash and 1 to excite the alt when the key is turned. you can get these alternators in just about any amperage you want.