I have a Merlin lll block. My old heads were 074 GM that had the bolt holes in the ports but were plugged. I just bought some new Brodix...so before I put em on should I just have them drilled and tapped for the extra bolts? It looks like Brodix marked the location with a drill but didn't go all the way through to the port .If I do this do I drill all the way through or just partial depth?