Kreb's Cycle maps for N. California will show many possible bike friendly options for your destination. Not necessarily as direct a route as 36 or 299. I last rode Amtrak to Dunsmuir and rode N. to Yreka and then West on Hwy 96 following the Klamath River to 299 for the last section before Arcate and Eureka. I followed the Coast Route home to SB from there.