My Dodge D60 used these springs/shims that retained the caliper. at the top and bottom of the caliper, you wedged a piece of metal curved in an arch between the caliper and the caliper support bracket. this is what retains the caliper and before you can remove the caliper, these "springs" needs to be removed. there are no bolts that hold the caliper in place like on a stock isuzu front end.

I'm not sure if your Chevy calipers are the same way or not. its prolly a pretty bad description, so let me know if i'm not getting the point across.

-Rob