I don't know about the 55, but a lot of us back in high school would mount them underneath the vehicle and parallel with the ground. You couldn't see them that way and they could be put anywhere you had room. The downside was if you were very distant from an AM station, you would lose some reception ability. I've also seen lots of folks put them between the rear of the cab and the front panel of the bed...attaching the base down on the frame. When they're down, you won't see the antenna and when extended it will work just fine. Remember a radio antenna in any vehicle has 2 contacts...one for chassis ground and one for the mast. FM radio (by the way) is a lot more tolerant of poor antenna design. AM radio antennas needed more deliberation in design. Good luck.

~ Jon
1952 1/2 ton with 1959 235 | T5 with 3.07 rear end