So with a 58 and 56 head and block combination, the bolt and plug is not used (and was never installed from the factory, btw.) That may be part of the oiling issue if your motor did have the bolt and plug installed. Here is the rub as I see it. If your motor had the bolt, does it also have the plug installed in the block? I don't know that it matters at this point any how as you have provided the rockers with oil from a secondary source so you likely only need a standard head bolt and I myself would not drill it (given that you don't need it).
