Yes, that’s the correct seal (WBL 1135) if you have solid back glass or an aftermarket slider with the flange on the frame.
I see your previous posted photo, so yes WBL 1135
Plastic sill trim is correct for an ‘85 Silverado. 1981 was the first year for the black plastic sill.
The Aluminum sills fit the ‘85 and IMO look better. Here’s them on my ‘84
SBC 350 5.7 w Holley 670 Starts great ! Idles sweet and low when first started, runs great also but the idle increases and revs high. Won’t kick down. Very frustrating!
Carburetor? Choke issue? Thanks for your input