It's a 9/16" bolt, this much I know. I'm not sure what the original was, since I hacked mine off when I installed the lift. I would have to guess it was a course thread, but just to make sure grab one of each.
Sorry I can't help more...
I got a Jeep, it's lifted and it's got crap bolted to it.
Color by Rattle-Can.
LO Jeep Club #111 [and not proud of it]
Red Jeep Club #MC399