I don't know why you think valves are not available for this engine but they are. Check Rockauto for one.
Ironically, I just picked up my rebuilt head yesterday from my machinist. (Yep, on Easter Sunday!) Due to a miscommunication (I thought he knew I was going to do the assembly) it is complete and ready to go. He checked all the springs in a spring checker and re-used them. I was just going to replace them as they're 51 years old but he said they are good. He checked the spring installed height and shimmed them as needed. he also reused the valves. I have not unwrapped it from the plastic shrink wrap yet but the head looks great! I had him install hardened exhaust seats and new valve guides. He used cast iron because he says the iron wears better than bronze. Whatever, I trust this guy explicitly as he's been doing this since 1962.
At first he did not want to mill the head for fear of screwing up pushrod and valvetrain geometry but I had him do it anyway. I chickened out somewhat so we agreed on 0.080. I really want this engine to be right and very dependable so I'm OK with spending the $ for a complete rebuild. I know I won't have to worry about it later on.
If you suspect a burnt valve, it wouldn't take much to pull it and get a valve job.
If only one hole is low on compression, you can do the old trick of squirting oil in through the spark plug hole and see if that brings the compression up in that cylinder. The oil will temporarily seal the rings to the bore so you could eliminate bad rings for the low compression.