Just discovered this thread. Did the same with my 2007 Yukon. Son-in-Law donated it to me, and it had broken completely. He still drove it from repair shop to repair shop, no one wanted the job. Says it drove OK, just had this "clunk" sound. The rear end is still attached by three trailing arms, so it didn't change much.
My Son is the Senior Welding Engineer at a well-known prototype automotive plant in SE Mich, and I agree "It pays to know a good welder". He did just the driver's side, and used heavy plates also. I still don't have the tank back in, heavy rust on all the fittings causing difficulties, but I am sure it will last a long time.