The 2004 Walters catalog lists the following road names for the Overton cars (all were $9.98 each):
D&RGW (green/black roof) - kit & RTR
Undecorated - RTR
Baltimore & Ohio (blue & cream) - RTR
Central Pacific (green/cream) - RTR
Colorado & Southern (green/black roof) - RTR
D&RGW "Silverton" (black/yellow) - RTR
CB&Q (Hannibal & St Joesph) - RTR
Illinois Central (dark green/black roof/yellow lettering) - RTR
Maryland & Pennsylvania - RTR
New York Central & Hudson River (Pullman green/black roof/gold lettering)
Northern Pacific (green/silver)
Oregon RR & Navigation Co/UP
Pennsylvania (maroon/cream)
Santa Fe
Sierra RR (Pullman green/cream)
Southern Pacific ((yellow/maroon letterboard/black roof/gold & red lettering)
Union Pacifc (Pullman green, cream)
Virginia & Truckee (green/yellow)
White Pass & Yukon
There were other paint schemes such as Battle Mountain, G&D over the years. And as described earlier, only the Sierra Railway actually had such cars. The rest are, at best, could-have-beens. But they do look sweet on our model railroads! I have both the Roundhouse and Ulrich (all metal) versions.
Last thought, pick yourself up some throw away cars and experiment with removing lettering and putting new decals on. As you gain proficiency, learn to repaint to suit your desires. It's a skill worth having, and fun to learn! You are no longer dependent upon waiting for the manufacturer to produce in the roadname you want. This is especially true if your chosen prototype never had the car or loco in question. Just don't start with your prize locomotive!
my thoughts, your choices