I am looking for a slip clutch for my SQ420 Bush Hog roatry cutter. My question is where can I find one that I know will fit? Are they made to some kind of standard dimensions? The input shaft to my gearbox is smooth with a shear bolt and is 1 3/8" in diameter. I have seen them anywhere from $55 - $130.

Here are a few I found...will they work?