We saw many street bikes on the TOW even in the rain, not that big a deal with highway tires. It is very well maintained. Dawson, TOW and old town Chicken are high lights not to be missed. Air down a little, watch for pot holes and go for it. It's more of what your comfortable with than tire choice. The long construction zones are much worse and unavoidable most of the time, but still not really needing aggressive tires. A descent set of 80/20 works very well. Remember your only going to be on the non paved roads a small percent (less than 2%) of the overall trip unless heading to the arctic circle. You will be amazed at the assortment of bike types up there. We saw a couple of guys on Harley softail stretch customs with the big 26" wheel front end. Actually we saw more Goldwing, Harleys and Metric Cruisers than anything. The tire problems we saw on the road were tube type flats and blow outs. We stopped to help a few guys with flats but they had extra tube and said they had things handled, all spoke wheeled.
Lunch in old town Chicken is great especially the homemade Pies. It's off the main road, don't miss it. You can air back up there if you came from Dawson.
IBA #7147 Current Bikes
2004 R1150R, BMW
2002 R1150R, BMW
1996 Road King, Harley Davidson
1994 FXR Superglide, Harley Davidson