There is a step in the inside diameter of the main part of the wheel. If you turn the wheel studs facing down and drop your new wheel center in, it will slide down to this step. Hammer the center in a bit and tack it in. Mount the wheel half on your axle and check it with a dial indicator. Adjust as necessary and burn it in. The face of the wheel at the studs was hard to get a good reading off of, so we measured off of some of the other features formed into the wheel and got much more repeatable results. This step conveniently yields about 4.75" backspacing when using a 3/8" plate center. Combine that with the 1.5" spacer and you get 3.25".
Remember that whole thing about 3 different kinds of wheels? Well apparently they changed from the commonly available -458 o-ring to some crazy non-standard military o-ring for these wheels. I thought, mine were in good shape and I could reuse them. After the first trip, I found that one was leaking so I bought a new set from Kascar. They are in the $15 each range. Don't order the -458 o-ring unless you have the 8 bolts. That o-ring is slightly to big in major and minor diameter, and the -457 would be too small in the major diameter and still to thick in minor diameter. Epic Fail for the genius who decided that McMaster Carr was just too darn convenient.
There are several options for the beadlock insert. There is a ton written up on this so I wont spend much time on all the different flavors. I got the HDPE inserts from Stazworks. They aren't the cheapest option, but they are much lighter than the rubber or mag runflats, you don't have to modify them, and they are much tougher than the PVC inserts. My friend Tom just had one of his PVC inserts break inside the wheel and the resulting death wobble was a sight to behold. There is enough flex to the HDPE that you can just lay the tire down and stand the insert up perpendicular to the hole. Step in the middle of the insert and it will pull it into an oval and pop into the tire. Then stand the tire up and step on the edge of the insert to rotate it into position. The first one took about 10 minutes. The rest took maybe 3 minutes each. This method uses no tools, no cutting, and nothing is under tension to pop loose and hurt you or the tire. On the other hand, you can probably get all 4 mag inserts for the price of one HDPE insert.
The powder coat that comes on the wheels is insane. Somebody needs to figure out what they use and put it on rock sliders. I got a big metal wash tub and sprayed them down with a heavy duty chemical stripper that says it removes everything including epoxy and powder coat. Wrong. Tried a GALLON of another brand. Same deal. It basically softened it just enough that the knot wheel on the angle grinder could cut into it. It still took well over an hour and a half of wire wheeling per wheel just to get the areas that needed welding or plasma cutting clean. Who knows how long it would take without all the nasty chemicals (which eat through latex, vinyl, and nitrile gloves in about 15 seconds. DON'T TOUCH ANYTHING). Go all out on the safety gear. Full face shield and a good respirator are a must.
Prior to painting the wheels, I sent them off to the guys at Charlotte Soda Blasting. They blasted them down to bare metal, but the baking soda media is pretty soft so it wont damage threads (or even etch glass). It also leaves a dusting of baking soda on the surface that stops the metal from flash rusting. The media is also not reused so there is no danger of getting the last guys rust, grease, and powder coat blasted into your project. A quick rinse of vinegar and water immediately before painting leaves a perfectly de-greased surface ready for finishing. I also followed up the vinegar/water with some denatured alcohol. With the fairly high humidity, the surface would start to rust immediately if I didn't get it dry quickly. The alcohol really helped out there. Had I known how painless and cost effective this was going to be, I would have skipped the hours of chemicals and wire wheeling entirely and had this done before we did the welding.
I had the back of the wheels painted at Maaco. The finish isn't spectacular in the really deep hard to reach, but also hard to see areas, but looks good where you can see it. I wanted them in Rescue Green, and it was going be very expensive to buy that color from either the stealership or Sherwin Williams. The rock rings are just rattle canned with Rustoleum Industrial primer and satin black. This is the stuff in the big silver cans. The rings will take all the abuse so there was no point in spending any more than necessary on painting them. Besides, I thought the two-tone look was appropriate for 3 piece wheels. If I were to do it over again, I'd get the wheel powder coated, but I'd still use Rustoleum Industrial on the rings. Touching up the rings is really easy that way.
I only built up 4 of these wheels. I have a spare that is a bias Irok 36-13.5x17 on a 17x9 soft 8 wheel with 4.75" backspacing. I don't feel the need to have a beadlocked spare and having a 16.5" wheel with no beadlock is asking for trouble since 16.5" wheels need high pressure to keep the tire seated. Having a tire for the same size wheel was actually going to create more problems that it could solve. The critical tire and wheel dimensions are virtually identical and this solution saved me some money with no real compromise in functionality.
I used 1lb of high density airsoft pellets in each of the 4 tires. I figured that as soon as I get mud in the wheels, the pellets would help compensate a bit, and it does. Wheel weights are probably better if you are wheeling in the desert. If you hit mud, the airsoft pellets make the ride home a lot easier.
These things are VERY heavy, but the offroad traction is amazing, they can take a beating, and the price is pretty reasonable.