Should I replace my TRUCK tires before Alaska trip?

1/4 inch tread is not much.
I would be looking at replacing them before your trip. Maybe carry one of the old tires as an un-mounted spare.
I would get some thing like the Toyo Trail Cat II LTs.
A single spare should be no problem.
Your trailer tires could be more of an issue along with a spare or two for it. Seems we saw more trailer flats then TVs and MHs this past spring.
There is many tire stores in the major cities in Canada and Alaska.