OK bigbird... I am gonna try and not beat you up too bad as you clearly are a newbie with only two posts, both of which in this thread. First off, check out the new members forum and post up a greeting there. Next before making a post like this one, utilize the search function. It will help you learn more without asking a question that may have been asked several times before. Some of the guys that have been here for a long time tend to get really irritated by that.
On to your question. First off, on a dual wheel setup all the wheels are the same, the front axle ones, the rear inners, and the rear outters. All the same rim, all the same size tire. The original tire size is 9.00x20. The biggest tires you can go with before rubbing issues occur are 14.50r20's or 395's. However these tires typically require wider rims. Apparently 14r20's will not fit as they are taller than the 14.50r20's. I dont understand how that can be, but then again thats the way some things are. The largest MILITARY tires I personally have seen on these rims were 11.00x20's. I'm sire if you look in the civilian market you can find taller. 46 inches is literally the tallest you can go before the rear tires start to rub against each other. If you are wanting to just stick with the tires you have but run them "singled" you have a few options. Since you want the deep side of the rim facing out, that narrows it down a little more.
The first option is simply pulling the wheels off and remounting one wheel per hub deep side out. This will keep the rear stance as wide as it was, however it will put additional strain on the bearings.
The second option is to flip the hubs so that the mounting flange is centered inward more, then install one wheel per hub deep side facing out. This is better on the bearings than the first method. Really the only special tools required to flip the hubs are a 3 inch hub socket and a Budd socket with a socket turning device of your choice powerful enough to break those lug nuts loose, the rest basic hand tools can cover.
Either way you are running 4 less tires thus reducing your potential maximum load capacity. Me personally, I would just leave them be until I got the super singles I wanted. Hope this helps, and before you ask how to flip the hubs, use the search feature