Lizzard Head is the name of the pass on 145, but I don't think there's a tunnel on that route. I suppose you need the Mtn Directory to be sure. I haven't driven it south of the Ophir turn off.
62 must cross some sort of pass between drainage basins, but it's not significant.
GM suggests an alternative NW to Moab, and then east on I70. It's longer, but avoids all passes.
There is a tunnel on 550, a bit south of Oury, that's signed 13-7. I remembered it from various videos, and found it on Google Maps Sat view by the gap.
While some tunnels cut under the highest point, saving a last minute steep climb, more often they are found in canyon stretches, cutting through a spur or ridge that runs right down to the river. These tend to be shorter, and not well known.
The main challenge on 550 for big RVs (and passing traffic) is the set of tight curves around Red Mtn. They are tight enough that a big rig might have to straddle the center line.