What size tubing is that? I was thinking of building something similar, if I have the time.
1 1/2 inch all around. 2" for the mount point end caps.
After seeing Big Blues rack.....Picking up tubing Monday and ordered the tire mount. Figured might as well build what I need.
If you need any info, let me know. Here is a link to the tire holder. The tiregate mount comes with 1 1/2 inch bolts, but you will need to replace them with 2 1/2 bolts if you use my design. As you can see from the pics, I still have plenty of room left in the bed for bags/other stuff.
Bed Mount Series | TireGate.com