I have a 1970 T/A that has Goodyear Polyglas tires from the early 70s mounted on original wheels. They are dry-rotting and splitting on the backside, but still hold air and provide a correct period look. Car is show quality and correct but I would like to be able to comfortably drive it more and longer distances then just around the neighborhood without worries of a tire issue. I'm trying to decide whether I should purchase new radials and switch out just the tires or buy another set of reproduction wheels + radial tires to switch out with the ones currently on it, or buy new reproduction and what I think are very expensive goodyear polyglas tires to put on the factory rims. Please let me know what your thoughts are.

Simple: if you're going to drive it around, then new radials.
Show It: then repros.
If $$$ is of no concern then do both.

[mic drop]

I have repro bias ply polyglas on one of my Challengers and it drives OK. Wanders on roads with wear and crowns but not too bad.
The issue may be moot at the moment, I have heard repro polyglas is back ordered now.