I've seen antennas installed on both sides. I think many dealerships back then saw it fit to install on the passenger side because it makes more sense than the driver's side. When you look at it from a purist standpoint, if it is a dealer installed option, really anything is correct. I've seen older heaters installed in some AD trucks probably because they had some old ones on the shelve and had to use them, nobody really cared back then so why should we worry too much about this stuff these days other than it can be a fun obsession.

1953 Chevrolet 3100
261 cu inch, sm420, 3.55 rear, torque tube still,omaha orange, still 6 volt, RPO green glass, side carrier spare, all done
In the DITY Gallery
Video of the 261 running

1964 GMC 1000
305 Big Block V6, sm420, the next cab off restoration