I did an axle conversion to 8 lug, electric brakes with parking brakes, and used the HMMWV wheels and tires. The problem I had was the parking brake cable was 3/4" from the tire due to the wheel offset. I had to use a 1" wheel spacer.
Here is the axle spec I got from engineered by Dexter. ( please be aware that some out there are selling a drop axle rated for 5K or 6K, but not at the spring center and hub face to spring distance needed. Dangerous)
7K AXLE,
DOWN RATED DUE TO BRAKES AND SPRING CENTERS.
72" HUB FACE, 40" SPRING CENTERS, TOP MOUNTED SPRING PADS.
3-1/2" X 1/2" TUBE
9/16" WHEEL STUDS ELECTRIC BRAKES WITH PARK
The other mods I did was to get rid of the tongue jack and put a 1/4" plate under the tongue and add a 5K rated screw jack. Converted to 7 way electric plug, LED bulbs, and put a 12" drop adjustable drop channel with ball coupler in place of the lunette. When putting the drop channel on you have to move the safety chains to the side of the tongue and add 14" of chain to reach truck.
I also converted another 105 to electric over hydraulic. When doing this, the hydraulic brake system must be flushed very well with mineral spirits. I had to rebuild a wheel cylinder and found the seal cups at the brake supply store for $2.00. I used tires and wheels from the M1061 flatbed trailer. They are the same 6 lug but 16.5" wheels and the tires are 36" tall. They stick out about an 1 1/2". I also did the jack removal and replaced with a screw jack. It weighs out at 2150 lbs.
The cost to do the axle or electric/hyd brake conversion was about the same. Roughly $950 a couple of years ago. I find that keeping the parking brakes is mandatory. You don't want one of these to get away from you.
I have new cargo covers, Check classifieds.
Good Luck to All