JB,
I just referred to my 24-week mountaineering plan and for the weeks you mentioned, it is Steep Uphill Hike with your HR in Zone 3 (AeT + 10-15 bpm). For a 1.5 hour workout, it includes 20 min warm-up, 20 min. of Zone 3 followed by easy workout for remaining time.
Hope this is helpful.