I have a heavy duty hitch on my 81 SD it appears to have been built by a welding shop as is very neatly done ,I will look at it tomorrow and see how it's attached I know that it goes forward far enough to block the filler plug for the differential I had to grind a special tool to get the top filler plug out when I had the differential flushed and refilled I sold the tool to the lube shop doing the work....
William Rogers....

P.S. I could do a drawing of it and scan it and email it to you if that would help........

[Edited by william rogers on 05-19-2001 at 12:50 AM]