The gun tractors and 15CWT were 101" with Fords 1/4" longer.
The F60T tractor was 115" and the C60X 160"
Here's a F60S 134 1/4" wheelbase with an extended chassis for a radar body:
And here's another with the remains of the body:
I've also seen extensions on 158" chassis too. Usually they were for special bodies.