dually rear end
You can tell with a tape measure faster than you can with numbers.
On a single rear wheel 10.25" Sterling axle, high part of the brake backing plate to high part of backing plate you will measure 54", the frame is 37.5" wide outside to outside.
On a dually that had a factory pickup box with flared fenders the measurement is 58" , the frame is 37.5" outside to outside.
On a factory cab and chassis the backing plate to backing plate measurement is 54", and the frame is 34" outside to outside.
On the cab and chassis 34" frame you can run dual wheels with the 54" housing because the springs are 3.5" closer together.
On the 37.5" frame you need the 58" factory dually rear end housing to run dual wheels.
The cab and chassis rear that has duals on it will not fit a factory pickup box truck without moving the spring perches. Once you do that you can not install the dual wheels because they will hit the springs.
I hope this clears the air, it is a confusing thing they did on the factory dually.
The only other option to put dual wheels on a single wheel truck is spacers.
If you are going to install the dual wheels to gain extra weight carrying capacity, I have been told by a very good driveline specialist that I am better to run single wheels for the loads I carry. The reason for this is because of the changed constant bearing loading when the wheels are moved out 2 inches.
If you are looking to look cool or add a little stability when towing a tag a long trailer that is not loading up the rear of the truck with huge weight, the spacers should be fine.
If you are backing under a heavy fifth wheel trailer, or going down to the rock quarry and get 3 or 4 tons of stone, find a dually axle to put the duals on the truck.




