i feel like i should keep this one secret, but i just checked and i'm 99% positive the 650 bolts will work instead of the 550 studs. i'd want to actually bolt one up to say for sure, but they are pretty much the same length taking into account that the head of the bolt compensates for a little bit of thread portion at the top of the 550 stud. 650 bolts: as stout as the APE HD CB750 studs, and torque the same. downside: studs make installing the jugs easier, as they hold the cylinders upright.