Slick 60's

I bought a 64 custom cab short bed, except it has no bed. How do I know if it was a wide bed or a narrow bed? Can a wide bed bolt onto the frame if it was originally a narrow bed? What years of beds will fit this truck?

Assuming 2wd in both instances, they will interchange readily, may need to add wood spacer blocks. '64/'66 on the Styleside, basically '50s thru 70's on the Flaresides.
Paul

Thanks Paul.