The stamped locks will be fine. Keep in mind the ribs on the lock only position the lock, it is the clamping force from the taper that does all the work. If you're really worried about it, Hughes carries 2-groove stamped, case hardened locks. They may work in the 3-groove valve.

http://www.hughesengines.com/Index/produ...mp;partid=10318

Its very easy to recommend the best parts when someone else is paying for them!