clutch fan or not?

I put a used fan and clutch on my 70 swinger 318. I overheated and the fan clutch never engaged. It was a Hayden #2747 which is about 3.3" tall and almost impossible to install on the water pump snout. The clutch is a 1/2'' from the radiator. I was looking for a replacement and I looked on the O Reilly website and they list a Murray/ Hayden #2947 which is a tick less than 2 3/4" tall instead. They and Napa get +$95 for these. RockAuto has them for $51.79+ shipping. Thought you should know. toolmanmike