76-78 Head, Rocker Shaft Bolt Question

I have a later model head, 3696447. I did not get the rocker shaft or gear with the head. My question is on the last rocker shaft bolt, instead of the earlier 7/16 x 14 bolt, it is drilled for a 5/16 x 18 bolt. I can come up with a grade five bolt but what about the rocker arm retainer. Do I need a retainer with the smaller diameter of the bolt. If so anyone with a part number or one to sell? Thanks