well you found the problem. usually the older ones work fine, especially if your wiring is well maintained.
if switching to the newer denso types, you should have a sense wire that senses the voltage at a remote spot (usually you hook the sense wire near the starter solenoid, or battery or headlight relay area, not at the alternator itself)... this allows the alternator to adjust the voltage to meet the demand at the remote spot. (has a volage regulator built
in)
with the older types of altenators, if your voltage regulator is good, then you will be all set.
however with your setup, the voltage regulator is not regulating anything and the alternator is pumping full out
