Like Dwyane said, 5/16 will be fine on 8mm. if you totally run out of options, you can grab some from AFR, as mostly everything they do is 8mm.

RIP Monte Smith

Your work is a reflection of yourself, autograph it with quality.

WD for Diamond Pistons,Sidewinder cylinder heads, Wiseco, K1 rods and cranks,BAM lifters, Morel lifters, Molnar Technologies, Harland Sharp, Pro Gear, Cometic, King Engine Bearings and many others.