I have recently rebuilt a radio for our 51 Chevy 3100. It works great now after replacing a few tubes. I would like to put this into the truck but have had difficulty locating the 1/2" nuts that mount the front of the radio through the dash. I have found 1/2" 20 threads but need a finer threaded nut. I would appreciate some help finding these nuts.

Thanks, Larry
1934 & 51 1/2 ton Chevy trucks