"The only reason I'm so curious of the valve guide, is that I can look in and see the valve is gummed up with oil."
Which valve? Intake or exhaust?
If exhaust, more likely rings.
If intake, especially down the stem, maybe the guide and/or the seal is shot. On "old" engines, the seals tend to go bad from age/use. IMO, a likely "contributor" to the oil burning. How much?????
I'd hate to see you spend a bunch of money for valve work, it the cylinder needs to be bored etc.
Since you have the heads & cylinders off, I'd mic the cylinder for wear, ovalness, taper etc..
See what you have in the "important" (expensive) area first.
Even if it can get by with new rings, I know I'd probably want to put "fresh" bearings in it too.
Valves & guides can get expensive, especially if you have to have them done.