My 59 Burb with a 307 V8 and a Dana type 60 3/4 ton rear end (3.73 ratio) and a SM 420 4 speed made a 2500 mile trip from California to Tennessee, towing a Datsun 510 station wagon. Both the van and the wagon were loaded clear to the roof with clothes and household goods. My wife was driving, following me with the bigger load- - -a 1970 Cadillac Fleetwood towing an 18 foot 3-axle trailer. My rig weighed 16,700 pounds. I got 5 MPG, she got 10. Drive 100 miles, gas up both rigs, and press on! That was in February 1980.
Jerry