The combat wheels are a split rim wheel designed for easy tire/tube
replacement or repair in the field. The wheels are easy to identify as
they have bolts around the wheel. The very early production MB's had a
solid one piece wheel.
The addition of the spare gas tank and trailer light connection could have
been done on your Jeep at anytime during it's life. These items were
commonly retrofitted during normal rebuilds.
My 1944 MB has an Army Air Corps compass installed in the dash. Although
it is impossible to determine when the installation was performed, I must
compliment the people who did it. The installation was done so well, that
it looks as though it is supposed to be there. I have even had other MB
owners look at my Jeep and not notice it at first. When removing the paint
for restoration, we found the familiar Strato Blue of the Air Force on top
of the original olive drab, so I assume the compass was installed during
the Jeeps time with the Air Force.
Good luck in your quest,
Andy
P.S. The engine number for the GPW was on the right front side of the
head, towards the front. Other locations are on top of the bevel for the
water pump.