HO scale decals by Jack Burgess are available for sale providing all of the lettering needed to letter any of the various passenger cars owned by the YV including RPO 107, combines 105 and 106, coaches 302-305 and observation cars 330 and 331. One decal sheet will letter RPO 107 and all three of the Beaver Creek passenger cars (105, 302, and 330). These decals were printed by Rail Graphics and are $8 per sheet including domestic postage; lettering diagrams are included.
You can purchase a set by visiting Jack's Yosemite Valley Models page. Complete details can be found there on how to purchase them.
(Image and text courtesy of Jack Burgess)