Call ahead to Fairbanks- Talk to George, owner of Trails End BMW ( RE dealer) ,Make an appointment to have your bike looked at ( you will probably need it by then) .Ask him if he has tires in stock to replace a K70, or trials or what ever parts you think you will need.
George comes highly recommended,don't make him mad, he might ask you to leave, he has a lot of work in the summer.
Oh I'm no tire expert, but most dual purpose tires are made of softer rubber to get more grip, everything has a compromise when asked to do more then one kind of job.