Steve,
As you pointed out, Chimbo will not really have a heavy carry, it will be steep but the altitude is the big challenge. Building your base is key which for me the bread and butter is the runs and the weighted carries. But in addition, I also like to do one High Intensity Interval training session per week. It could be run up a hill for 30 seconds, or run on a treadmill, or run a lap on an outdoor track. I use work to rest ratio of one to one, meaning if I run for 30 seconds then I rest for 30 seconds and then I repeat for however many sets I’m doing. These sessions generally last from 20 -30 minutes for me and I often incorporate it into my runs.
Also, I tend to dial up my aerobic training a little but by adding in one or two sessions of stationary bike. I’m a bit older so my joints cant take all the runs so I add in a session of bike to keep my heart rate in low zone 2, high zone 1. I usually put on Youtube and watch something or listen to a podcast as I crank away.
Finally, if you can get there a day or two earlier to Quito that may help acclimatize but this is often a tough one given our schedules!
Small things like becoming more efficient on your steps help too, the less energy you can use up the more you have in reserve.
And stay hydrated.
I’m not a coach so those are just my 2 cents!