Pushrod Guide Hole Elongation
If a higher lift camshaft (.440+) and/or higher ratio rocker arms are being installed the guide holes on the head should be elongated to keep the pushrod from hitting the top of the guide.
The head should be off (a lot of metal filings will get in the engine otherwise).
Not all of the guide holes need this, just the ones that go all the way to the top of the head.
These guide holes should be ground (slotted) toward the rocker stand.
Try not to make the guide hole a lot wider.
One other thing to check is the pushrod guide plate, it may need slotted also.