This is getting to be a rather common problem these days. Machine shops think 60 year old machines should operate at the clearances of modern engines and they never bother to look at the old books. Whenever I work a head, I shoot for the big end of the spec. Using a quart of oil every thousand miles ain't nothing compared to valves seizing when they get hot. We even went for the big end of the speck back when we were expecting to get another 100k out of a head. These old engines will never be driven like that and with today's lubricants, the guides aren't going to get any bigger with a lot of miles.
