Even in the fifties, when "plastic Jesus" was a very common sight in my area, most of them came with a magnetic base but had to be GLUED ON to stay in place. The only place a magnet would stick on most US made dashboards even then was the "lid" on the ash tray down at the bottom of the "dash," and sometimes on the sort of rounded "cowl" that covered the base of the steering wheel hub where they added - at about that time - that newfangled optional thing called a "turn signal." (Most locals never did figure out what that option was for.)
A briefly popular accessory from the early 50s was a sort of "bean bag" with a small steel plate in it. You could toss it almost anywhere, bean side down, and stick your "magnetic accessory" to the plate. Unfortunately, when the beans shifted, Jesus took a tilt that made it look like he'd just come out of a street brawl, but at least he wouldn't fall off the dashboard.