Hello Lionel,
Don't worry about hijacking the thread mate. Would be good to have everything on the one heading for the 1. 1/5 L/L Chevs.
Getting back to your rear brake light, I would guesstimate it is original or close to it as far as year of manufacture goes. Mine had smaller and more conical shaped ones which I believe are avail on the reproduction market if you wanted to compare them.
http://www.oldchevytrucks.com/cart/i...g%2FTaillights
These show other types. Seems to be a lot of variants unfort.
Cheers