Did a little investigating this AM. I really think the rear reservoir is for the front brakes (but I am really second guessing myself). Its tough to trace the lines in that back corner as there are a bunch of wires, little fuse panel and what looks to be those lines that are abandoned down on the frame. The larger O.D. brake line goes to the rear of the MC and looks to T into the front. I put some fluid in both bowls (front brake lines VTA) and pumped the brake a few times to see if there was anything leaking out at the back end. Nothing... Ran some fluid through it but of course it only wants to come out of the drivers front as its the first open port. Thinking about getting a brake bleeder pump and going around one by one with a temporary small threaded hard line attached to the rubber hose so I can connect the bleeder to it. I agree at the minimum this MC needs a cleaning, will look into rebuild kits. What about the Booster, should this get replaced or do these rarely fail/degrade? Its an ugly looking sea life piece but if it works I don't need beauty (want this truck to come off as a work truck).