Your '50 3600 should be 36" wide at rear, spanning the outside of the frame rails. Same as the '54 detail shown above and as noted below in the 1948-51 Shop Manual data. Unknown if the hitch listed by fester that is used for a 34" wide frame would work for the 36" or not.
~ Dan 1951 Chevy 3 window 3100 Follow this story in the DITY Gallery "My Grandpa Carl's Truck and How it Became Mine" 1966 Chevelle (Wife's Hot Rod) | 2013 Chevy Silverado (Current daily driver) US Army MSG Retired (1977-1998) | Com Fac Maint Lead Tech Retired (1998-2021)
