Does the A/C clutch disengage properly? Remove the belt and see if you can turn the outter pulley by hand. If not the clutch on the compressor is bad. What type of belt are you using? Smooth or ribbed on the side that rides in the groove? Try using belts from Oreilleys. How far down does the belt ride? The belt may just be expanding too.
Brake cleaner?
Take some sand paper and run it through the groves. Use a very harsh grit. You some something that will grab the belt.
One final thought:
I'm doing the conversion mine. You have to relocate the A/C compressor and the alternator. Change the water pump to a reverse rotation type. Add a pulley to the crank, water pump and the power steering pump. I don't like the smog pump option so a find a setup with out one. Complete systems can be found on
www.ebaymotors.com
Here is a website where you can buy an entire used system for $200.00
http://www.tacreationsusa.com/bracke...ccessories.htm