1973 valiant 318 car stalls when compressor comes on

Don't just guess MEASURE it. There is NO excuse in this modern world to NOT have a multimeter. You can buy them several places "in town" or over the internet. 50 bucks can buy a really decent one, HorridFreight a few dollars can buy a cheap but useable one. YOU NEED a multimeter if you are going to work on these old girls

And, you may be wrong.......are you sure the alternator wire ONLY gets hot when the AC compressor is on? Seems like it would take a long time to do that, and if it heated that badly, there would be fuses blowing or "wire smoke." Does the compressor clutch wire get hot? it is much smaller.

MAYBE the reason the alternator wire is getting hot is some other reason.

Does the compressor clutch even engage? Does it operate when the engine is running? You can HEAR the clutch engage, "loud click" and if the engine is running, you can SEE the compressor run (look at center of pulley hub)