Tonneau covers and caps from what years fit?
 

I'm looking for a used tonneau cover on Craigslist, on my old 6.5' bed GMT400 I had one from a GMT800 and it was about an inch short but still worked, does anyone know if the bed of a GMT900 or maybe ram or f150 was the same width and length for the top rails of the bed? I found one for a GMT900, does anyone know if the bed dimensions are the same?