According to the restoration package that I ordered from Chevrolet, a 60-66 1/2 ton is 78 3/4 inches wide at the door handles. And a 3/4 ton is also 78 3/4 inches wide at the door handles. The 3/4 ton is going to weigh more than a 1/2 ton because the entire chassis is built with sturdier metal and bigger components to handle the extra weight it can carry. 3/4 ton trucks from that only came with an 8 foot box. Only the 1/2 tons could have the 6 1/2 foot or 8 foot box.
Drew
