Get some beer and sit down with Satelite views on Google Maps. You can create custom maps and put pins on the maps where you see tire tracks. Then if you have a decent phone your GPS will even tell you how to get to them. That is how I found 90% of the trails I hit. You will see the double tire tracks from Jeeps in different places.
On a different note, I heard Centralia is great, but I havent been there myself.
Complete rebuild axle/engine/everything swap in progress:
Parts already gathered for assembly: 2001 Ford 302, 1990 Mustang GT 5.0 ECU and wiring, NP435, NP205, Pair of axles from 04' F350 SuperDuty (Sterling 10.5 Posi rear, Dana 60HP Front-Both Disk Brakes 3.73 Gears), 37" H1 Tires, 9" lift TJ Coils for 2 link conversion in front, Stage 2 Clutch Kit, 3 Row Aluminum Radiator, Chevy Astro Steering box (4" front Stretch), XJ Rear Leaf Springs (6" Rear Stretch), and lots more.