The chrome rear-window-seal retainer (lock bead) is for "dress-up" purposes. Chrome was not originally used. The retainers for all three rear windows are installed on the outer side (as described by Vern) in the same way (but only described in the Shop Manual for the "main" rear window).
If you mean by "chrome" the reveal moldings, on GM and Chevy trucks it came on 42 and 52,53,54 and on.
