Two rocker shaft hold down plates for a SB

That's a really good idea for hold downs, do you have to use a jam nut to keep them from backing off any? I've come to the conclusion that Fastenal is pretty much just Hobby Lobby for men...

I just use std grade 5 nuts, no locks because you don't want the stud screwing out of the head when you take it apart. Never had a problem with them coming loose.