My heads had to have the boltholes tubed since I had them PORTED heavily. I had to have 2 of my studs turned down on the lathe just enough to allow oil clearance through those 2 bolt holes.
If you buy new Edelbrocks, they actually send you 2 turned ARP bolts with the heads. I didnt use them, since i used studs, but im guessing even without tubing the holes, 1/2 inch may be a hair big for proper oiling.
If this is what you mean, I'd be happy to send you those 2 ARP bolts supplied with the heads.
Edit: here's a picture of 1
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