Not sure about the '46 but Jim Carter sells them for the AD bar. I got em for mine there. As I recall there are two types of brackets for the AD trucks, older and newer, as well as Chevrolet and GMC versions of the bracket to fit the different cross members. Mine was the older Chev style (47-early 51). The older style rubber parts might be the same for pre-'47.
For comparison with your bar you can see the various parts on my brackets here in part 5 of this post.
http://rustyfiftyone.com/ketchup-catsup-catch-up/
