To summarize where I'm at with this before moving on, having maladjusted/ possibly burnt valve(s) coupled with marginal high-altitude fuel issues MAY explain all the issues that I've been having with this 235 engine. When this engine gets into "running on 5 cylinder" mode, it could be the gasping of fuel starvation just short of stalling out or a valve sticking temporarily. Or there could be something else going on as well. I'll just have to see.
Thanks everybody for your help! Dave

1946 Chevy pickup, 1948 Chevy suburban, 1950 Chevy pickup, 1952 GMC pickup, 1957 Chevy pickup, 1939 Chevy pickup