Radial threads have .3125 holes before they are tapped .
3/8 10 are .308 at the most .
3/8 10 regular ( V threads , not flat bottom ) will be really lose on that shaft.
Radial should fit fine but you have to watch cross-threading it .
Double tapping has increased in popularity since c/f shafts have arrived.
Some users have been lucky and some have not. If it's cross threaded, it tears the threads. I personally don't advise it. It's Just not good machining at the end of the day.
McDermott 3/8x10 joint screws have a .281 minor between the threads.