a/c compressor bolt

[57 chevy]

ANYONE KNOW THE SIZE OF THE BOLT THAT COMES THRU THE SUPPORT BRACKET THAT MOUNTS TO THE BOTTOM STUD OF THE DRIVER SIDE HEADER, GOES THRU THE BRACKET & THRU THE ACCESARY BRACKET THRU THE COMPRESSOR & THREADS INTO THE BOTTOM OF THE PORK CHOP LOOKING BRACKET ON THE FRONT OF THE COMPRESSOR. MINE MUST HAVE VIBRATED OUT & GONE. IT LOOKS TO BE ABOUT 41/2 INCHES LONG. MY PARTS BREAKDOWN DOES NOT SHOW THE BOLT, BUT DOES SHOW A NUT AT THE FRONT, WHICH IS INCORRECT BECAUSE THE PORKCHOP BRACKET IS THREADED FOR THE BOLT. NO MODS TO THIS AREA OF CAR, I AM THE ORIGINAL OWNER. WAS CHASING THE RATTLE @ IDLE PROBLEM & THATS MY CULPRIT. ANY HELP APPRECIATED. THANKS