Pacing without a Powermeter

Ideally yes. But it will be all but impossible to stay in that zone on the long steep climbs. Here, you may stray up into higher zones. I find it helpful to have a heart rate alarm that goes off if my heart rate gets too high, and then I make a note to slow down - which sometimes requiring grinding out a very slow cadence in easiest gear. Also - go with your 36 cassette!