Pvmt-Pndr, do you think the engine is running ok?, I drove a lot of 366 and 427's in city beer delivery, our single axle tractor/ trailer combo's were 32000 -48000 lb. plates and had no problem with that weight and getting it rolling, even on the big road we could go 65 - 70mph. This was back in the 1970's and 80's so they were all Holley 4bbl. carbs. it wasn't until the late 80's that we changed over to diesel. I have no clue what the axle ratio was but tranny's were 5spd with 2 spd rears.

1957 Chevrolet 5700 LCF 283 SM420 2 speed rear, 1955 IH 300U T/A, 1978 Corvette 350 auto, 1978 Yamaha DT175, 1999 Harley Davidson Softail Fat Boy