Working on a `53 3600 and cannot identify what went in (one) of the two holes below the drivers side mirror holes (outlined in red). I'm certain one of those holes is for the aerial--can't figure out what the other hole is for ?? Looking at photos of the cab before the body work, there is an aerial mounted but no other hole present.
I cannot discern the red outline, but I can see the two "additional" holes in the side cowl. My guess is that those holes were use for a radio antenna that used two attachment "stand offs".