Yep, the front and rear bumpers were different, with different part numbers (Front - 3700438, Rear - 3700469). As you noted, the rear bumper is "flatter" with less curvature than the front. Can't recall if the rear was a option on all models of trucks. I'll look at my RPO list when I get home tonight and check.
By the way, if you don't own one yourself, here's an online copy of the
1929-1954 Master Parts Catalog . Great reference.
