I agree with you, Denny. I got the information from the Chevy Truck ID Numbers book from Cars & Parts.
Rolf, the numbers listed are for the HO52 and HO72, essentially the same axle with the main difference being the brakes. They were manufactured by Eaton for Chevrolet. As noted, GMC used Spicer axles during that period, as did some Chevrolets with the leaf spring option, usually Camper Specials.
