7 blade 17” fixed fan vs 6 blade 18” clutch fan

You don't have an AC water pump pulley-do you? All of the cars that had AC, both big block and smallblock had a 6 vane water pump and a smaller water pump pulley. Possibly if you have the 8 vane water pump and the AC water pump pulley, could be some of the problem. When I got my 71 Polara in my avatar running, I thought too-the 18 inch 7 blade fan would be good, but being an AC car-it had that real small water pump pulley. That small pulley just can't pull that big aggressive fan without slipping and squealing. I always hated clutch fans. I ordered a new Hayden HD clutch and installed it on the original fan and no more belt slippage. I'd welcome any opinions.