The HT style 3-pt requires the frame rail extension past the rear axle. That extension is where the pivot blocks for the cross shaft are installed. If a Large Frame tractor does not have the frame extensions, you have to use the lighter-duty 3-pt that was offered for the early Large Frames like the 1250, 1455, etc.
I've got manuals for both the 1886 style p/n 18010 and the HT style p/n 18086. Here's a picture of my 1886 3pt hitch. It uses push rods whereas the HT style uses a single lift lever and is set up different. I don't think the 18010 would work on the HT series. Also a picture from the parts list of the 18086 so you can see the difference between the two.