1996 GMC Truck

Electrical problem
1996 GMC Truck V8 Four Wheel Drive Automatic 220000 miles

in this truck, I have a new battery with a good charge, and replaced the cables, replaced the alt. With another 70 amp rebuilt unit, still not charging, belt tention is good, I can charge the battery to full charge, and drive the truck till the battery drops to around 10 volts, at which time it starts missing, and eventually cuts off, engine was recently rebuilt, I dont know what to try next, the manual suggest replacing the fusible link, also the gauge never really gets above 10 or 11 volts, even with a full charge, everything else in the truck is working ok as far as I can tell.
May 29, 2010.

Remove alt and have it bench tested. Could have a bad unit, wouldn't be the first time.

Jun 16, 2010.