Valve locks....
You can actually get away with using the 5/16 locks, are they bead lock or square groove? the other option is to have the keeper groove area centerless ground to .310 to .3105. It is probably still cheaper in the long run and would allow you to get parts easier in the future. I would reccommend using steel locks if they are square groove.
That is the reason we used 5/16 valves in our new heads.


