I suspect they where molded onto the stalk. There is a serrated spline and a deep grove near the top to prevent rotation or pulling off.
In the Florida sun most cars get hot enough inside to bake brownies, or to fry an egg on the top of the dash board with a black colored Teflon cookie sheet. With a black interior it is hot enough to melt some plastics and cause a second degree burn (blistering of the skin) if you sit in the car wearing your Daisy Dukes, or for those male beach goers your spandex swim thong.
Back in the seventies it was a common weather report time filler; if it was a slow news day. The weather is easy to report in Central Florida as it never changes from mid June through mid October. It reads as high eighties along the coast, with afternoon thunder storms forming along I-75 (you can set your watch by the thunder storms depending upon where you worked or lived). Temperatures will be pushing mid nineties inland away from the coastal sea breezes, with a smaller chance of rain due to the entrenched Bermuda high creating strong easterlies.
I think it was the Chamber of Commerce or the County Commissioners wanting to sell prime swamp land real estate to folks from the North East, that asked the TV news shows to stop doing those fried egg stories as it painted Central Florida as being uncomfortable to live here. Everybody here lives in an air conditioned house, and drives their air conditioned cars to the air conditioned malls; so I have no idea what they were talking about it being uncomfortable living here.
I have pulled off the shifting knob from three different column shifted Camaros and Novas going from first to second speed shifting my six banger before I converted it over to a V8 powered beast. The heat loosens the grip on the knob and they slide off if you are gripping them hard enough. (I even pulled the shifter stalk out of a 1964 Chevy II once doing that; breaking the pot metal shifter collar on the steering column where the rolled pin went through it). Thought I was going to put my fist through the windshield after it happened; which was stronger than the rear view mirror pot metal mount that I sent flying out the passenger side door's window.