as the title reads, i was just wondering if anyone knew the bolt size that runs thruogh one side of the linkage, going through the bottom of the shifter, and coming back out the other side of the linkage, where a nut meets it to tighten... i lost the bolt on the highway jus now as my linkage dropped to the ground

 

I know it's a 12mm head and nut size. Not 100% sure without checking my tap and die set, but I think it's a m8x1.25 pitch. If your shifter is setup anything like mine, there might also be spacer washers to take up any extra side to side space where the linkage bolts to the shifter.