Apologies to the purist in our company.
My stock fan clutch was dead and I was beginning to get the worrisome heat spikes in traffic and off road. After researching the alternatives I decided to try the GM unit (....research seldom leads to GM, I know....) I made the decision based on: availability, effectiveness and finally- cost.
I installed the $42 super duty (I think that's what it's called) GM fan clutch in my 96 D1 about a week ago and I'm happy to say it works like a charm. The noise is considerable at low speeds but that's because of the huge volume of air that is being moved. As the truck reaches hwy speeds the noise is hardly noticeable.
My heating problems are gone- which certainly would have happened with a OEM part as well- and I'm happy with the way it has worked out.