Running boards? Good luck. If you find a good set of used ones snatch them up.

Most end up cutting and welding 1/2 ton boards together to get the proper length.

Superior Glass Works lists them for 3/4 ton truck. Might be worth a call if you don't care if they're glass.

http://www.superiorglassworks.com/Running-Boards-Smooth-1947-1954-Chevy-Truck-p/53t04.htm

1954 3600 Chevy Truck
"The Fake Truck"
In the Stovebolt Gallery
More pix on Photobucket