In 1980 my wife followed me from central California to Nashville Tennessee in our 59 Burb, towing a Datsun 510 station wagon. I was driving a 1970 Cadillac Fleetwood and towing a 3-axle backhoe trailer with a gross weight of over 10,000 Lbs. with all our household goods on it. The car/trailer combo weighed out at 16,700 Lbs. when we got an over-wide permit at the Arizona border. They didn't weigh the Burb, but it was loaded to the gills also. The Burb had a 1970 307 V-8, a SM 420 4 speed, and a 3/4 ton Dana type 60 rear end from a late-60's GMC in it. I got 5 MPG with the Caddy and the Burb got 10 MPG for over 2500 miles.
Jerry