That seat nut should be internal not on the outside of the tubing. I think all Mb`s from 43 onwards had the spare wheel rest fitted so yes there should be a pre drilled hole however a lot of repro jeep panels come without holes.
Been looking into these for a while but no joy identifying what they are. Tried US militaria forum and no help. I thought muzzle covers, they measure about 4" wide by 7" long. Any ideas?
Have a look at this link https://forums.g503.com/viewtopic.php?t=171612 Talks about higher numbers, might help. Is there any over paint on data plates? if not it may suggest they have been of before repaint.
I had a similar problem with a jeep that had sat for 18 months. turned it over but didn`t get any fuel to the pots. Tried everything but no joy. towed it behind the van and it fired after about 10 seconds! not sure what the problem was but doubt e10 would be the reason