LS swap alternator issues

[todd7498]

Hi, I did an LS swap in my 72 last year and have had alternator issues. Alternator charges fine until I turn on the A/C and it sucks the voltage down unless I rev it up, head lights or electric fans don't bother it but the A/C really seems to pull the voltage down. If I rev it up a bit and keep it around 900 plus rpm it seems to be fine. Any ideas? Thanks

Possibly I need a bigger alternator? I think mine may be the 105amp, I am running a stereo set up with a couple small amps, and dual electric fans.