Why not just cut whatever is there, to make a mounting point, to weld a reciever to it. They sell those reciever sized square pipes, that're made just for stuff like this.
Warning... this is a HUGE problem. I have spent countless hours trying to solve this and have had to make some CRAZY modifications. FYI lowes no longer sells the hitch adapter? WHY?
HiSun claims the adaptor is standard but itās not. I finally found and extension adaptor at Harbor Freight that would fit into the socket but had to drill another hole to get it to line up so the pin would fit.