the one thing im not sure of on your car is were the voltage regulator is. if its controled by the computer that could be the issue. if its in the alternator like most are and i figure yours is then its in the wireing. something must be shorting the regulators in the alternators and doing the same damage each time. what amp alt are u useing? what brand name? does it seem like the belt is to tight? any odd wear patterns on the belt? check all wires connecting to the alternator as far as u can, look for any stress or heat signs worn or partially broken wires.

 

RPM's shouldn't kill an alternator. I take mine past 6k with no problems at all. And a bad belt, or a misalignment isn't going to fry the innards either. Those could cause a belt slip, belt chewing, or bearing wear issue, not an electronic one. Check all your connections and make sure nothing is shorting out, or even close to any metal. I know the hot lead on the back of the alternator can sometimes be a close fit to brackets and such. Check the boot and make sure it's well insulated.