Quote Originally Posted by Martin in Bellevue
This has been discussed before. The restricted coolant holes keep the coolant volume in the head. This is a good thing, as the head is more evenly temperature regulated. The holes on the exhaust side are for oil return to the pan. You can leave the headgasket uncut for installation.

As an aside, check the old headgasket between cylinders 5 & 6. I caught my headgasket before it let go, in a pre-emptive headgasket replacement with new valve guides & a mild cam regrind. There was significant decay between 5 & 6 on the old head gasket.
How were your coolant holes at the very bac of the block? I think these are the most at risk from blocking with any cludge.

If you can, post some good pics of the block surface before you put your HG on, you could get some very salient advice