Are you towing the bus or towing WITH the bus? We just welded an short piece of 2" square receiver tubing to our bus along with a "U" shaped metal plate. We tow our 5500lb Jeep Grand Cherokee 4X4 "four down" with it (no tow dolly so we can't back up). We have a long drop receiver ball because the bus is so much higher than our Jeep.
The tow bar on the Jeep is a Stowmaster 5000 (one person hookup and you don't have to be aligned up perfectly, just get close... wonderful!) with hidden brackets. I bought both from two separate sellers off of Hitch Trader
"for sale" section. I do love those self-aligning tow bars. Took me several months to get the tow bar and the correct brackets for my Jeep at the price I had budgeted. I never remove my tow bar, It stays folded up on the Jeep all the time.