I have a 94 with a 302 and I was looking into a underdrive pulley to increase power. Are these worth the money and can I still use A/C if I do install it?

 

The only changes with an underdrive set such as that from Troyer Performance is...

Crankshaft pulley diameter decrease
Waterpump pulley diameter decrease
Serpentine belt length decrease

All other pulleys remain active and the same size. You loose no accessories. I did mine when I installed the Troyer eFans so I can't be exclusive about commenting on increases in MPG or power. But, I can say that throttle response is drastically improved (likely due to the eFans more than underdrives). And there is a noticeable difference in acceleration. It took all of about 15 mins.

 

Just make sure that you don't involve the alternator pulley. Other than that, you should be fine.