cylinder heads / reaming valve guides?

Is this a car you plan to keep, or are you doing this to sell it to somebody you hope you never meet again?

IMHO the guide is the most important part of the head, don't cheap out here. Everything is referenced off the guide bore. I've never had really good luck with the K-line type liners (had a couple migrate). I would suggest thick wall replacement bronze of even iron guides.

As for valves with oversize stems, if such things exist I can think of no good reason to use them. And many bad things come to mind.