This if it works is an image of a caster shim installed in a truck like yours. They need to be the same on both sides and as you can see they are wedge shaped. I don't know about the dimple so not much help with that.

http://www.classiccarsandtools.com/wp-content/uploads/2012/08/4_IMG_2116_comp.jpg
I hope this helps some. Can you post a picture?


Steve H