I have just replaced them on my ’35. A problem was that I couldn’t find exact replacements for the channels and most of my originals were in bad shape and not salveagable. The available window channels are either too tall and stick into the window opening or are rubber covered rather than bright stainless on the edge. If you can get a decent inside measurement you can see what might be out there, primarily at Restoration Specialties and Macs Ford.
Mine were screwed to the wood framing with #4 wood screws with slotted heads filled with detritus. I got some out with a screwdriver, but definitely not all.
An alternative if the channels themselves are okay is dig out the felt and replace. I did this on my Jaguar several years ago as the felt was available by itself to reline the channels. I haven’t run into that elsewhere, but you might look at the Moss Motors XKSUnlimited site.
Haven’t dealt with a ’20’s car, but I think they were pre safety glass. Does that make them thinner with narrower channels (less than 1/4 inch)?