I just lifted my truck last night and went through all of this. You need a 2" 8x6.5 to 8x6.5 backspace adapter and 4" suspension lift on a M1008 when running the 37" x 12" x 16.5" HMMWV bead-lock wheels and tires. You only need them in the front for clearance, but it looks a little goofy in my opinion to only run them in the front. I will be getting spacers for the back soon for mine. You need them up front because without them the wheel touches the tie-rod end on the driver's side. You may also hit other things when turning, articulated, etc. But just putting them on the wheels hit and won't seat without doing some pretty serious rubbing. The other option is to get wheels with re-centered hubs to correct the backspacing issue. I paid $114.50 for two of the spacers and got free shipping here:
Billet Wheel Adapters.com Wheel Adapter Super Store. NOTE: you will need to supply new lug nuts to mount these to your axle when using these spacers! Your stock lug nuts will not fit into the hole in the spacer. I didn't figure this out until Sunday night at 1 am after working on my lift for 5 hours. Had to drive around all day with 37"s in the back and 31"s on the front! Urgh! NAPA doesnt stock a lug nut that has a small enough head to fit into the hole with a standard thread. The lug nuts and posts that come on the adapter use a metric thread and are to mount the wheel to the adapter. I had to go to the local Firestone shop to find a metric hex lug (that's all they had that would fit) but with standard threads that was small enough to get into the hole. Also, only a thin walled chrome socket will fit in there to mount these. Finay got it all wrapped up tonight and I ABSOLUTELY LOVE IT! Truck looks awesome, rides great, goes faster, handles tighter, etc. Hope this helps. I will be posting pics of my build in another thread soon.
