Hi Chris,
I assumed you were ok with most of the holes but wasn't sure. Those series of holes do look pukka don't they but I can't for the life of me think of any jeep installations or add ons that would have needed them, suggesting they are from post war use.
Have you tried asking the question on the G503 forum? If there is an answer, someone on there will have it.
cant think of a good bodyman as I replaced the back panel on mine with PB in the garage but if you find one, let me know as there will be some MW wings and a footstep generator box to sort out soon.
Did the MWR body you used for your MW have a data plate by any chance?Have you got a photo.
Do you also have any photos of the floor showing the fixing arrangements for the operators seat at the front?
cheers