With the info we dragged out of you it seems he wants to get to the Oregon coast and drive a short distance to Newport. If he is in a hurry and isn't interested in the views or quaint settlements, the answer is 126........
If he wants a great drive and will be returning to Redding, I-5 north to the highway that follows the Columbia River from Victoria, WA to the Astoria Bridge South to Newport. That way he can see the entire coast by leaving Newport and continuing south to 299 and then over to I-5 and north a few miles to Redding.
I have been going up to Florence since 1949 and the DW and our DDs have been doing it since the mid sixties and we had a cottage in Yachats for a long time, we've driven everything from a VW bug to our current rig with a tow. Non of the roads are a big deal, it's only big deal on how fast you drive.