Two sources, either of which should either inspire you or else convince you to look elsewhere for your prototype:
Model Railroader's October 2005 issue contains an article/trackplan for Gary Hoover's Cajon Pass layout.
Great Model Railroads 2005 (also from Kalmbach) leads off with an article/trackplan for Ted York's Cajon Pass.
Both are impressive. Neither is for the faint-of-heart. But there's a starting point for you.
-- Paul