You are going to have to do better than this, link to the auction or a part no or something?
Generally, the large reservoir is the rear half, goes to the front (disc) brakes. If the cylinder is to be used on disk, the disk end normally does not use a residual valve, drum brakes do.
Several people have posted on installing the $170 GM booster for Mopar A's setup, with photos. They had to trim the rod a bit to not hit the firewall. I expect all cars use the aft reservoir for the front brakes. I don't think the residual valve is essential, and I don't have any on my Dart (I think) since using a later MC/booster from a 95 Breeze. I think they are mainly required today in hot rods that install the MC under the floor. I read that they haven't been needed since they changed the wheel cylinder springs to have cupped ends to load the rubber seals.