Chances are.......... you HAVE A BAD BATTERY, are wiring it up wrong, have a short somewhere, bad hot or ground connections, buying from a bad vendor.
Get a rebuilt
Delco1. It's not the Halogen lights.
2. Alternator has a regulator.
3. 63 or 75 is enough output unless you have a lot of accessories all at once.
4. The alternator has it's own cooling fan. It is a huge aluminum heat sink also being cooled by radiator fan and forward air flow over it. It's NOT over heating.
5. You don't give us the part number and vendor of the alternators that went "bad" ...........so we can't investigate.
6. You have provided no basis and no testing to be able to say "alternators are burning out". If all you know is the battery is dead....look at the battery, check the output of alternator at about 800-1000 RPM and note above comments by the members. Alternators are a "brushless" design using slip rings. Alternators have an exciter function and residual magnetism to start output right away at pretty low RPM.
I have not considered having a starter, alternator, generator or any dyno/motor rebuilt except by me (which is seldom) for a long time. Too cheap and easy to buy and have delivered to your door or get at a local FLAPS with lifetime warranty. To me, sending to a shop was necessary at a time long past. I consider it a DIY or buy.
