Kenneth, is there any reason I could not use the third member from one of these 17200 series rears in my old 52 gmc 17501 housing. The hollander shows they use the same gasket(3rd member to housing) so the bolt pattern is the same. It also uses the same side gears so it should mate up with my original axles. Am I missing anything. I need a third member anyway and this 17200 series has a lot of gear options available. It looks like the 17800 has the same gearing options as the 17200. Any thoughts?