Good find!!
A lot of people mount then on the sides, and such, but here's what I did, I didn't use the tailgate anyways, and don't have to worry about knocking them off with trees.
It's about the same layout as a M38.
FYI,� My finger is only there to hide my plate number, and yes the spare is flat. That happened 30 min before I took the picture, lol!

The M38 tailgate has extra support built in, so yes, it does need backing.
I just used scrap angle iron to build this.

Hope this gives you some ideas!!!