There were 3 major manufacturers of the step side bed. California Step Side was one here on the west coast, they splashed chevy truck step side fenders in fiberglass and had steel step plated in the front of the fenders. Nothing on the rear. Anderson ????? in the south also made a step side package, beds were actually made in Anaheim, Ca. They splashed the late 50's, 60's fenders. I don't know who made the bed and fenders with the molded in step front and rear for GM. All beds were installed by new car prep division. I remember seeing the beds stacked up and the trucks without beds waiting to be fitted. What amazed me is how painted in two different places the paint always matched.
I vaguely remember something about the tail gate hinge and chain / latch being different between the two. I have a picture of a 76 with the Cal step side that shows the difference in the fenders. If it is not posted on
www.photobucket.com/v8luv, I can post it. The picture on cts post is a factory stepside.