I ordered one of the E-body clips (6002976) and compared it to the C-body clip (6002734) to see if it could work or be made to work.
I feel as-is they will work but I might open them up a little.
If you look at the two there are two differences, 1. The threaded portion isn't as deep, keep in mind that is the entry point for the screw, might take a little effort to get the screw to grab a thread to start. 2. More notably is the flange, the C-body one is taller with a bend in it.
When you insert the C-body shapes to the trim and fits snugly.
With the E-body clip it fits a little looser but does grab both edges with no worry of it popping free.
Once fully inserted the E-Body clip holds itself in place, you may need to bend the wings to add a little pressure.
You can see that the treads are about 3/32" into the trim (it is reduced some as the E-body clip is shorter), not sure how much of an issue that might be.
So for those needing these clips I feel that the E-Body clip is a suitable replacement in lieu of original C-body ones.
My 69 Polara has 24 of them.
Alan