Piddling around on the webs, I ran across this Hayden fan clutch info sheet about the ubiquitous GM HD fan clutch they sell, p/n 2747. There was a discussion a few months ago about using the 2747 and 2947, and the difference but I'd never seen a comparison side by side pic. The 2747 clutch fits MOST standard rotation, bolt-on GM V8 applications over the years without breaking the bank (it fits some dodge, ford, plymouth and jeeps, too). Check to make sure.
The ONLY difference between them is the shorter shaft on the 2947 allowing you to put a thicker radiator in your car without having to do major surgery. See below. They both use the same HD clutch head.
Either will work if it fits your application, but unless you're putting in a fatter radiator and need the clearance, or plan on doing it in the future, just stick with the 2747 if stock with HD cooling.
The ONLY difference between them is the shorter shaft on the 2947 allowing you to put a thicker radiator in your car without having to do major surgery. See below. They both use the same HD clutch head.
Either will work if it fits your application, but unless you're putting in a fatter radiator and need the clearance, or plan on doing it in the future, just stick with the 2747 if stock with HD cooling.