I'm gonna say 5/16 for both. The holes in my bedside (in the garage waiting to be patched up) are 3/8, but typically bolts have a little play around them for alignment. Also the holes in the tailgate hinge that shares one of the bolts will not take a 3/8 drill bit. An 11/32 bit fits, but not the 3/8.
Shoot a PM to Mar-Ktech. He'll be able to tell you for sure.
Last edited by klhansen; 11/23/2015 6:41 AM.