Thanks Denny, but knurling is actually not an option, I've heard numerous times it's only a short lived remedy. I will be using roller rockers, so the wear on the valve guide won't be all that strong, though, but it should turn out a high mileage motor, as this engine is going into a 1970s Impala, which is just undergoing a full "like new" restoration (the other engines I'm just doing are for every day use)...
What do the others think of knurling? I'll have to measure the worn guides to see if knurling is an option anyway, ALL of the valve guides were passing oil (had no positive valve stem seals).
At goodson I found a reamer that will drill out from .343 (that's 11/32") to .500 in one go. Piloted of course. It costs $ 130. Is that a good price? I think that's the way I will be going. But I someone says this tool is available from somewhere else for half the price I would be glad to look into that
THX so far,
Max