Spend the money and you will never need to worry again.
The manufacturer of the 12 pin military socket is BarCar, in Illinois. The socket is only available with the square yellow zinc mounting plate. Order the plug with the 7 or 4 wire leads necessary to accomodate your trailer connection needs. Unless you want to use some old beaten up 'cut off' from a junk truck and cut off the non-required leads. I have attached a color chart to show where the leads wire up to the plugs.
Originally I had a Hummer with a 7 pin RV style round connection, so I spliced in a 7 pin plug to the BarCar 12 pin socket. Wrapped up the wires and now have a functional adapter that requires no changes to either the tow vehicle or the trailer.
Now I am purchasing a Jeep Wrangler, and had to make another to accomodate the Jeep's 4 pin socket.
The new socket will run you $65, shipped. then buy the 4 or 7 pin plugs. They're like 3 or 4 bucks. 15 minutes worth of splicing and you're done.
OD Iron sells the reverse adapter, so you can plug the adapter into a military vehicle and tow a civvy trailer.
Make it yourself or pay someone to order the parts and make it for you. They are going to be around $90, to have one made. But who said that collecting military vehicles was a cheap hobby?