In reply to DaveMo:
Climbing is not an endurance sport, using "endurance" in the way that cyclists/runners and so on use it.
The biggest limiting factor is local muscular endurance in the forearms, which is as stated above dependant on capillary density, NOT on the ability of the body to transport oxygen.
> What I want to do is get the effort level right (grade, intensity rest time bla bla) so I can selectively train power or regular endurance.
This is why almost all training plans prompt you to set the difficulty level of routes/problems based on your experience rather than physiological measures such as heartrate, or even perceived exertion - it's mostly things like "problems that you can onsight" for 4x4 endurance exercises or "problems that you can do in a few tries"