Installed on a '78 F-600 water carrier. The 24" should cover pretty much anything with duals. I had to snip an inch off the top. This is easy to do with a table saw, but a handheld chop saw will work too. Then use a utility knife or carpet cutter to cut an inch or two thickened perimeter so the mounting pad is flush with the top. Two pieces of 1" x 1/8" x 24" zinc plated steel (on 18") made from clamp bar building materials. Four 5/16" Nylock bolts on each side complete a good installationβ¦