I am having my neighbour machine a set of tubes to come up out of the rocker to take a push on breather, I've ordered a couple of K&N breathers and we will get that done next week when they come in.
Today I pulled the rockers off and checked the dimension of the oil passages. On the BBM heads I have they were able to take a 1/4 threaded plug so I tapped them and threaded in a pair of plugs. When I vacuumed up the little bit of tapping debris the restrictors came flying out. They are far too small for the passage in a BBM head.
Having never built an engine before I didn't recognize how small they were compared to the oil passage. They are probably sized to a different head. In any case, passage is now stopped and the rockers are back on.