Recommndations Re: OR, WA - NSXPO Driving
Two possibilities come to mind:
1. A short loop off I-5 adding about 1.5 hours: Little Panoche Road to Panoche Road to Highway 25 to Highway 198 back to I-5.
Other loops are possible in northern California, e.g., County Road 306 south of Corning. But those are close enough to home for you that you could do them another time. South of Sacramento is territory you don't normally visit, so it's better to do your excursions there.
2. What would be REALLY cool is an overnight at the Hacienda Guest Lodge in Fort Hunter Liggett. There is simply no better place to park yourself and your NSX for the night. And you can go explore Del Venturi Road and Nacimiento Road and be back for dinner in an hour. Links:
http://gocalifornia.about.com/cs/hearstcastle/a/hacienda.htm
http://hacienda.newhalltelecom.net/
http://www.californiamudholes.com/TheHacienda.html
The Hacienda is close to the midpoint of your drive and you will really appreciate the visit, especially if you can get there by 6 or 7 PM and have dinner at the restaurant (which is open until at least 8:30 PM). For this option, I recommend Highway 198 over from I-5 to King City, then Jolon Road to Fort Hunter Liggett. For the next day (following the dawn patrol of Del Venturi Road and Nacimiento Road), it would be G14 south to Paso Robles, then Creston Road to La Panza to CA 58 over to I-5, then freeways all the way to Phoenix.
This excursion should scratch your 2-lane itch, and it will cost about 4 to 5 hours total extra, plus the dawn patrol (all the way to Highway 1 for the hard core, about 45 minutes each way). I guarantee that the Hacienda will be a revelation, and that it and its surroundings will be the highlight of your trip to Phoenix.
One sub-option is to do what I do: take an evening patrol on Del Venturi Road and have everybody take the dawn patrol over to Highway 1 on Nacimiento Road. Get started by 6:30 AM and you will likely have Highway 1 to yourselves. You'll get to San Simeon in no time, and you can then turn inland on 46 to Paso Robles to Creston to La Panza to 58 to I-5. G14 is a fine road, but it's hard to turn down the chance to cruise Highway 1 at full speed.
I can post some photos perhaps next week from my Tour de California 2005, when I drove all the roads mentioned here, except 198 and 306.