1) No problem for the information on the replacement dust brush rings. I'm unsure if Aerus still carries them--it's possible, because it still sells the exact combination tool (minus the logo)--but I've seen them on eBay and on different vacuum parts websites before. Here's one, but you'll want to do some research before you make a purchase:
http://onlinevacshop.com/product/dust-brush-insert/. You just need a flat-head screwdriver to pry the brush ring out and push in the new one until it snaps in place.
2) Combination rug/floor tool w/side wand lock tab ... You should be able to swivel it, so the tab is on top. If not, maybe the wand lock was replaced at some point without placing the tab on top. While the honeygold brush plate is original to the Super J, it's also possible that the swivel connector may have been replaced at some point with an aftermarket one--is the "This Side Up Electrolux" decal the same? Following is a list of combination rug/floor colors (holder/bumper/brush plate) that will help with identification of original parts. Keep in mind that the brush plates were painted the same color as the tank bodies until the 1521s; then they were just brushed aluminum. Further, sometimes colors (or primers) were different between the standard and budget models--two that can be easily confused are the more metallic teal of the 1205 and the flat teal of the Model L. That's getting really picky, isn't it?
Furthermore, there was an on/off gleaner switch on the side of the head from 1954 (E, EA, T era) to c. 1967 (tan G--some of them have the switch and some don't).
-blue/(no bumper)/hammertone blue - E, EA, T
-ivory/gray/pale gray - F, R (early)
-ivory/blue-gray/blue-gray - S
-ivory/teal green/aquamarine green - aqua G, R (mid-late), ivory L
-ivory/tan/tan - tan G & L
-teal blue/ivory/teal blue - teal 1205 & L
-ivory/ivory/honeygold - GJ, SJ, honeygold L, 1363
-ivory/ivory/brown (w/plastic swivel connector) - Oly One, brown 1453, tan 1451 & 1451E
-gray/dark gray/metallic gray (w/plastic swivel connector) - Silverado, gray 1453, gray 1451E
-sand/sand/aluminum (w/plastic swivel connector) - 1521, DJ & Marquise labels
-lt. sand/lt. sand/aluminum (w/plastic swivel connector) - 1521, Grand Marquise, Legacy, Ultralux, Ultralux LX, Ultralux Classic
3) The Super J was manufactured from October 1975 - April 1979. The 50th Jubilee (Golden J) sold from 1974-75. That motor was also used in the Oly One and Silverado. It may also have been used in the honeygold, brown, and metallic gray model CBs (commercial canisters) and the period's uprights.
4) I read somewhere that Electrolux first outsourced its motors in 1984 during the end of the Silverados and beginning of the Diamond Js. I don't know how long they continued to be, but supposedly the Marquise had a problematic motor along with some later 1521s--if not all of them.
5) Regarding the small changes (e.g. the bumper logo ink colors) I agree that it's next to impossible to obtain accurate information on all of them. As you mentioned, some early SJ photos included the bumper logo colors of the 1205. Even the manual editions may contain shared photos instead of each having its own. Kirby and Hoover manuals were known for photo sharing, too. It's a cost effective measure for sure.