Recently I through out the old ext. reg'd 65 amp alternator that came in this '70 El Cam. I read about the CS130 here in the Tech Archives and so I purchased a unit from a web dealer known as NQS.com; National Quik-Start. They have redesigned the rear housing of the std, GM design to incorporate a quadrant of cooling vanes to dissipate heat so that the ambient engine heat won't shorten the alternators life. It sounded good to me, so I inquired there with a guy by the name of Randy to find out about the mounting compatiabilty of the CS130. After a few emails he indicated that the alternator would mount with no prob's; he was right about the pivot boss and the tension boss and I knew from the tech archive the third mount to the back of the housing (the anti twist mount is what I call it)would have to be altered. I asked him about this and he assured me he could rotate the housing so that my ex. spacer would mount to the anti-twist mount. Wrong.
I had to go to an alternator shop and find an old bracket that was correct for spacer length, then cut,grind and drill a hole to mount the anti-twist bolt thru to the predrilled hole in the housing. Minor pain in the ass, but what they hell, I was looking at a 105 amp v. 65, so it seemed worth it.
2 months later on a hot weekend in San Diego I see my H20 temp go to 205 after some city stop n go and brief shut down and restart,then the re-circulating cools it back down to 180.
Later that night driving home I notice the electrical sys seemed weak and slow; 2 days later my batt. is dead.
My guess is that by rotating the housing to accomodate the third mount bolt, it puts the regulator side closer yet to the head and headers, combined with the heat of the day and fired the regulator to an open circuit.
Result: as long as the batt. is connected, the system being drained by the open circuit.