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 guides need this, just the ones that go all the way to the top of the head.
These guides should be ground (slotted) toward the rocker stand.
This only needs to go down about 1/2" to 3/4".Try not to make the guide a lot wider.