Someone on another forum site was able to help out with photos. Apparently, Roseville is incorrect in their part description.
This is how their description reads:
Quarter Window Rear Channel Rubber inserts E-Body. PAIR. 21 inches long, flocked inside.
70 E-Body Quarter Window channel rubber strips-PAIR, hardtop and convert. this was a 1970 only, some 71 built cars do have the brackets on the outer wheel house but 71-4 did not use.
I checked my '70 Challenger convertible, and the brackets (#28 in the diagram) are NOT there. Therefore, I don't believe these were ever used in convertibles. The build date for my Challenger was 11/14/69. I've attached photos courtesy of Jess T.