Car Code for Brakes

I'm looking at the '73 Shop Manual under disc brakes. The table listing the rotor thickness separates by car line. What is "R-W' and "B-J' in the table? Typically "W" is Challenger and "J" is Coronet/Charger. "R" is Windsor, "B" is Hamtramck. But the combination of letters is throwing me. Would they have used a different rotor spec for a disc brake on a Charger at the Hamtramck plant than one built in any other plant????:realcrazy:

OK, now I think I can post all of the attachments to illustrate why I'm confused about this and why it matters to me. I'm trying to get the front suspension/brakes correct for the '73 duster. I don't have a Plymouth Service Manual, but I do have the downloaded version of the Dodge Manual. The front suspensions should be the same for the Duster and the Dart, so I want to follow the instructions for the Dart in the manual.

In the intro section of the manual, there is a carline identifier. Here it is.
Carline Designation1024_1.jpg

Caline designations are L(Dart), J (Challenger), W (Coronet/Charger), and D (Polara/Monaco). So far, so good.

Now, I go to the Torsion Bar section. This is it.
torsion bar procedure1024_1.jpg torsion bar procedure1024_2.jpg

This section purports to cover P,D,C, Y and R carlines. There are NO P,C, Y or R carlines in the carline table above. Moreover, there is no instruction for torsion bars for the Dart (L carline).

Aside from the confusion in the service procedures due to this, I have another reason for wanting to nail this down. Go to the Brakes Division of the Service Manual section here.
1973_Dodge_Disc Brakes1024_1.jpg
At the top of this page, I want to find the correct front rotor thickness, minimum thickness, runout, etc for the Duster/Dart. Note that the manual gives specs for "R-W" and "B-J" carlines and "all except R-W and B-J". What the hell is R-W and B-J???

Maybe I'm just dense and my novice status is on display, but this make no sense to me.