I would use the originals before a generic Grade 5/8 bolt. Flywheel/clutch bolts are a fairly high stress application. Also note that it's the correct length, so the pressure plate bears on the un-threaded portion of the bolt shank. You never want a sheer load bearing directly on the bolt threads.
'65 A-code coupe, T-10 4-speed, 8" 3.25 limited slip
Last edited by stephen_wilson; 07-19-2019 at 05:21 PM.