The Stovebolt Site Forums The Shop Area General Truck Talk 1949, 3800 sidestep,how to post pictures

QX
Stepside, maybe? That's a common name for the "old" style bed with the fenders on the outside, and usually an outside step as GMONIZ shows. For a 49 like yours it looks like this
http://www.stovebolt.com/gallery/norris_cliff_1948.htm
And in this case it's the running board as you said.