It's called "fabrication".
I called five shops today and all of them referred me to a place called Fabworks. I left two messages but didn't get a call back. Apparently, when a job like this has to be done, even the hitch shops, which only install hitches already rated for whatever, aren't able to do this because it's considered a fabrication of a new design. RV shops told me that while they have welders and had included this service in the past, liability companies stopped insuring them if they continued, so now only specialty shops will do the work. "Monster Garage" comes to mind, although I would prefer to go to an "You've Been Overhauled" type shop. Will have to wait til next week to see if this can be done. If not, does anyone want to buy an Airstream MH?
1992 Airstream 300LE, rear queen, Banks Power!