Are you looking to stay all original? If so then bias ply are the way to go. If you don't mind straying from all original radial will be safer and better at high speeds. I'm no expert but from what i have been told radials will technically fit on some of these older wheels but can fail since they were not made for radials. So if you go radials it would be best to also get new wheels that have the lip on them for radials.
There are radials sold like diamondbacks that have the bias ply look if you want the benefits of radial but still want to look original.
Personally I like staying original so I'm in the process of ordering some for my 37 and sticking with bias ply since I don't drive it a lot and I stay off the freeways. I'm a newbie to the pre war Era so hopefully someone will chime in if I'm wrong.