If the mfg recommends a specific stud then I would use it. If they don't I'd measure the bolt hole and use a stud which fit the head and had at least 1.5D worth of thread engagement into the block. 2D of thread engagement is probably better but you need at least 1.5D. So for a 7/16 bolt you want at least 3/4 of an inch of engagement and 1 inch would be good.

Another engineering rule of thumb is that you need 8 full threads of engagement to transmit 100% of the torque. On a 7/16-14 stud that is 8/14 or 0.570 inches of stud engagement. But you need to add a safety factor to that since there is usually a chamfer on the top thread.