1968 Radio mounting hardware

[sts1985]

I have a 1968 GTX which I'm restoring. I have the thumbwheel radio, however, I do not have the 2 bolts that secure the front of the radio to the dash. Does anyone know what size and depth these boots are or where I can purchase these?

 

[65-440]

I want to say 1/4x20 , my radio has been in the car for a year now. I went through the same thing, as far as depth I think 1/2 to 3/4 ....