We drove our 1990 345 from Montana o Anchorage late in the 2018 season. The coach had 107k on what is the original drivetrain as far as I know. Mechanical issues:
1). Had new headers installed the day we left Missoula. Picked the coach up as the shop was closing, and realized that we had a dead miss by the time we got out of town. Replaced plug wires to no avail. Replaced plugs the next day and all was good.
2). When we stopped for the day in Teslin, YT, found that the little round plug in one of the tag axle hub covers was missing, and he grease cup was rattling around loose inside. The town mechanic took the wheel off for me and found that the cup had just fallen off, axle and bearings were good.
3). Trans cooler line developed a leak about halfway into the trip, had to add about a quart of trans fluid daily.
4). Cooked the front rotors along the way, had a nasty shudder when braking when we got to Anchorage.
The biggest problem that I found as far as the drive goes was frost heaves that would sneak up on me and catch me going too fast. Bottomed out the front suspension many times with no apparent damage. The Canadians are pretty good about marking those with signs, the Alaskans not so much. The worst section of the drive for those was the highway from Tok to Anchorage. If you have the time, the road from Tok to Fairbanks and then down to Anchorage is much better, that is how we drove back last summer on the way to the ferry at Haines. The highway is paved all the way, we did not get hit by any gravel. The scenery is spectacular, I kinda want to do it again.