84 Buick T-type Electrical

I have a 84 Buick T-type, ran okay for many years, then alternator went out. Changed that and battery, ran fine several times ( I only drive it on week-ends, project car), disconnected battery to prevent drain, reconnected battery, alternator dead, new alternator bench tested, battery charged up. Any idea why first two alternators died? Connections all appear good. How would I check for a possible short?

I have found that alot of re-man alternators and starters suck....If you have a gauge to read the volt in the car keep an eye on it... after the car is started the volts should drop down to 13 or 14 volts