If you're going to Crater Lake, I would suggest that you head out towards Medford, then Grants Pass and 199 over to Crescent City on the coast. From there you'll head north and your adventure will begin.As was said before, all of the state parks were full as of last year, you can make res a year in advance, but there are a lot of REALLY nice private parks and most are about the same cost as state parks.
As far as 199 is concerned, I have pulled my 35' TT and Excursion both ways and my 40' Tradewinds with toad from Crescent city and had no problems.