i have driven the alaska highway going on 11 times and it has gotten better since the first time i drove up in 89.
i for one have never had a problem with the borders, the canadians have always been very friendly and have never asked for money
.
and the road is very good until you get to alaska then it gets a bit sketchy.
a friend and i drove up a 72 914 and loved the trip never got a flat and the locals are easy to deal with.
i stayed in toad river on that trip called ahead to the lodge told the keepers we where running late and they would be closed when we arrived.and the lady said she would slip a napkin under each door that was vacant and we could just enter the one we liked and pay her in the morning. nice people.
i would say take a full size spare if you can or put on a set of tires that are sold in canada so you can get a replacement if needed.
i recommend doing the trip if you can as its an awesome trip. i think the best time to run is September as the colors are good and the roads have less traffic.
cheers ed