Is there a reason you won't take I80 to 20, 20 to 101, then 101 up to Crescent City?
Most of the road to Grass Valley is 2 lane, some ups and downs, then once pass Grass Valley mostly flat until you cross over I5, then some minor climbs before Clear Lake.
From Clear Lake it is mostly flat until you hit 101. Then mostly 4 lane up to Eureka, and then some 2 lane near the coast until you hit Crescent City. Lots more to see on that route than going up 395. 299 is mostly fixed now but before they fixed that section it only had 5 passing zones going out of Whiskeytown and all 2 lane with hardly any pull outs.
2006 GMC 2500HD 4WD 8.1
2018 Outdoors RV Creekside 21RBS