We just completed the Alcan 5000 Winter Rally in Feb/Mar (seems so long ago now). During the rally, we completed the entire length of the Alcan, the Dempster (including up to Tuk and also out to Aklavik on the ice road), the Dalton up to Coldfoot, and then down to Anchorage. Fuel was plentiful, even being winter. We did have 1 location where the fuel station was shut down with no power and a few people ended up needing a little of the carry fuel. We were driving a 2dr Rubicon in 4wd most of the way and got around 15mpg overall. We did fuel up on the Dempster on the way back down from Inuvik (at the Arctic Circle), mainly because we didn't stop at Ft. McPherson (station didn't open for an hour or so and we had a lot of miles to do that day - ~730). Fueling with a jerry can at -30f is fun. The crappy CARB nozzle snapped off inside the tank. Combination of the filler design on the Jeep and the plastic not liking the very cold gas. Ended up emptying one of the jerry cans at the Arctic Circle on the Dalton too, figured why not, had to use them up to ship the vehicle back.
Bottom line, while there can be some distance between fuel (as they say, never pass gas on the Alcan), as long as you pay attention and know your usage, you'll be fine without carrying a tanker's worth of fuel. If you have an aux tank, I would carry a spare fuel transfer pump instead of the jerry cans. The extra weight (especially up high) and hassle of them wouldn't be worth it in my mind. Carry a Milepost and go through each of the roads you're planning on taking, highlight all the fuel stations, there's quite a lot.
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A couple of videos