A 33x12.5 tire probably isn't safe to run on the outside. It will stick out very far. I went to a former Jeep dealers house with my 71 once. When he saw my side mount tire he asked how many times I'd knocked it off. Guess it used to be pretty common to rip them off the side of the trucks. And that was with a skinny 7.50-16 mounted.
That being said, the bracket to mount the tire on the outside of the bed is the same one Jeep used to mount the tire on the inside of the bed. You just mount the box (same box/carrier a CJ used to use for side mounts) on the inside of the bed instead of the outside. Though I don't know if a 33" tire would clear the bed floor.
Tadsal was making a real nice custom fit tire carrier for J-Trucks, might want to send him a PM and ask if he has any.
1987 Cherokee Laredo 2-Door 4.0/AW4
1971 Gladiator J2000 Platform-Stake Dump 350/T18
1970 Gladiator J3000 3407Z Camper Truck 350/T18
1968 Wagoneer Custom 327/TH400