I started measuring on my old 50's Semi-Cab. It was about 6-feet 9-inches wide. It was a bad tape-measurer but I think it was pretty accurate. Its another 3-inches on either side of my ranger's cab, so I think it would be too big for a mini-truck, unless its sectioned. I might just stick a 48' Ford Convertible cab I found in the woods on it.
I found a crappy 76' Lincholn with a 460 for sale, I'm thinking thats what I'm going to use to build my Lincholn/Mercury convertible. Plus the fact that its an actual Ford Smog-"Monster" is pretty cool. Should be able to push my massive convertible along pretty good. And its the right width (Their both like 8-feet wide)
I can also keep some of the funky Lincholn body on there too....I could actually just use the back-portion of my Convertible and keep the Smogger front, and It would still be wild looking.