Looking through my collection of pictures from unrestored cars I think we may have a situation where there may have been two suppliers and in turn possibly two different finishes.
Color of the springs as mentioned appear to vary between two different paint color - may relate to a running change . Did not take the time to look that possibility up in the parts books. For the pictures I did include some cars built at other plants (with the cast iron intakes) since these brackets and springs would have been installed at the engine plant and not the car plant.
Found three with the aluminum intakes. Of course the brackets we sometimes moved or rotated by owners that wanted to increase throttle pressure. You might see some possible patterns to the installation and the variances in the bracket finish as already been discussed
8T021J115xxx Bracket does not appear to have been zinc or cad IMO since it held up poorly when compared to the plated finishes right next to it on the carb. Most of the ones I found do not look plated a silver like finish though we do find both used
8T03J180xxx
8T03J192xxx
8T03J194xxx
8T02J198xxx
Other two plants and out of sequence because of that
8R01C167xxx
8F01J2167xxx
Hope this helps
