We use a tool box from tractor supply. I believe it is 48 inches wide. It is just a chest that we mount to the inner fender wells during hunting season to use as a lock box for guns and other stuff. I have put one in a cj, yj, and tj. Its not perfect in terms of it sits high on the fenders and makes it so the top does not open all the way. You can cut the bottom out and make it the same shape as a lip box for a pickup, however then you can't fit a long rifle/shotgun in because they have to fit diaganoly. But we still fit most guns. Remove the handles to prevent rattling, and put a sleeping bag in the bottom. Remove when season goes out.