'72 Scout II Charging Problem

["Shubin, Pete" <PShubin@domain.elided>]

Does a '72 Scout II with an AMC 258 I-6 & T-18 have an external voltage
regulator?  If it does, where is it located?  All the wiring (what's left of
it) except for the headlights is stock.  Here's my problem.  

When my Scout is not running and the battery is charged I get 12 or 12.5
volts at the battery and at the alternator.  When the Scout is running I
still get 12 or 12.5 volts at the battery but 35 volts at the alternator.
My ammeter always reads in the middle or slightly to the left (discharge)
depending on whether the lights are on or I'm starting the engine.  

I had an extra new 70 amp large housing alternator I bought for my Blazer
and installed it in the Scout but still get identical readings from before.
I installed a new battery (exchange under warranty) and still get the same
readings.  The problem is the battery slowly goes dead as it isn't getting
enough charge from the alternator when the engine is on.  Any ideas?