Since AC is not "required", it would seem that any ac compressor should be legal as it is not a "performance" issue. I would view this in the same way I view a cool shirt box or fire system. They are not required so any version of them is legal.
I do not know about the alt. however, I suspect the answer is you must use a stock one so others do not go out and spend money on some ultra light (expensive) version.
There are ways to have removable side windows to lower race weight. This allows the window motors to go away as well. Likewise, the wiper system can be removed without too much effort to get rid of race weight and put back in as necessary. There are certainly ways to remove the dash, and a ton of wiring weight, without spending more than a few hundred dollars. I forgot, have you removed the head light motor system? There are ways to have a manual pin to hold the headlights open when required.
Big Dog