I used the lunati longer ones (5/16 & 3/8) & the up top 3/8 stud part is 1&3/4 (iirc). Down below it has way more than 1/2" thread length engagement on the bottom 5/16 stud section. With an 8" pushrod I can get minimal (OK) (~.020) preload with the rocker screwed down 6.2 turns (from 90 deg at zero lift per the straub vid with the cam lift I have) so there is a 90 deg angle at half lift. THE PROBLEM is the 1.6 chebby stud mounted roller rockers are too long & the roller is way too close to the outer (exhaust) edge of the valve. I dont want to at the moment relocate the stud & even if I did it would highly likely on the other side make the pushrods rub on the wall (they're close now) & I might even as is need to slightly file the pushrod wall to thin it slightly for a hair more clearance.