Per Google Maps, the suggested non-ideal routes are all about the same. If all the roads are open the fastest route would be to take 120 at Manteca and cut through the valley and out on 49.
120 Route - 17 hours, 21 minutes.
NA's SIL Route - 18 hours
Alternate iSm route (using 140 to Mariposa) - 18 hours, 10 minutes
iSm route (using 140 all the way into valley then out on 41) - 18 hours, 16 minutes
So, assuming that 120 is not completely available (or would be worse driving than you want), I'd probably take Steve's route simply for ease of driving (generally less windy) and you get to see a big landslide that took out the road and requires a detour over the river. It requires a big ass climb out of the valley to get back up to the cabin, though, so if road conditions suck that could be annoying.