Clutch fan noise

The unit seems to be squealing under high RPM but otherwise seems to be functioning fine.
(Small block AC car)
Belts are tight so I don't think its belt slip.

Any suggestions?

BTW what is the accepted clutch unit for the small block AC car? Thermal, Non-thermal, heavy duty?

Sounds as though the clutch unit is going bad or not disengaging at high rpm and causing the belt to slip. Can you move the fan blades back and forth toward and away from the radiator? If so the clutch is bad. I run a 7 blade stock fan with the heavy duty thermal clutch on my 340's. 90* days with the A/C on in traffic they never get over 200*.

No movement on the clutch while twisting the fan. I took the fan off and the unit is a non thermal unit. I thought that was odd for an AC car.
Car does not over heat at all in fact its really cool.

Any one know what is supposed to be on a small block with AC?

I had the same situation (SB A/C), that got worse as time went on at lower and lower rpms.
I replaced the entire fan/clutch and the squealing was gone!

When I was young and didnt know better I had a camero in Germany. Fun on the autobauhn. But I ended up with a noise from my clutch fan. It wasnt easy to get parts there. I called my Dad on the phone and asked him about it, he said you should replace it. Parts being hard to come by there and expensive I waited. About a week and a half later fan came off when driving and went through the radiator.

Replace the fan the clutch is going.

Well what should I get a non thermal unit or a thermal unit or a HD one?