Go the extra miles and take 140 if you need to avoid 120. Could take a different route up vs down if that helps.
I personally would take the fastest arrival time as I have been up-down all three of the west entrance routes without issue. Ok I am a bit slow up some of the grades and I don't consider that an issue.
+1 for going slower and using a lower gear. Also don't ride the brakes to maintain a steady down hill speed. More effective to coast up to the speed limit (if appropriate) and then use the brakes moderately firm to reduce speed 15 to 30 mph. Then coast up to speed again. Braking before the turns is best. The firm braking will better distribute the heat load to all disks and drums on all axles.