For the ascent, aim for same as a standard flat marathon, about 85% or so. Faster folks will probably aim a bit higher, slower folks should aim a bit lower.
Note that once above treeline most folks have trouble maintaining that target unless they have done a lot of high elevation work.
For me, the target is 160 (185 HRmax). The hard part is keeping it lower than that in the first 4 miles, the crowding results in this "I must get in front of that guy" mentality that results in many folks regularly hitting 95%+ of their max and blowing up in spectacular fashion by Barr Camp (if not sooner).
For the downhill, rule #1 is to keep the rubber side down. After that you give it whatever you got.