I know asking for opinions can be dangerous LOL, but what the hey... My son's '65 'Cuda has the 73-76 A body discs and 11x2.5" rear drums, and the stock 73-76 disc/drum MC. As the weather has warmed up, it has had a more frequent issue of the pedal going much further down than normal at random times. After one brake activation, it is restored to normal operation until the next random occurance of the same long pedal push. There also seems to be a lot more leakage from under the cover now, which did not seem to happen in cool weather. (Yeah, it is the newer stamped cover type and gasket.) and I drove a 3-4 of these cars back in the day, and never had MC leakage. We found that someone in the past put the distribution block (no, not a factory prop valve; that is separate) on the underside of the subframe. He routed one of the front brake lines from that block towards the header right beside it, and then turned it back to the outside. That line's loop is covered with reflective insulation but not other part of that block and lines are shielded from heat. We are surmising that the fluid is boiling a bit in and around the distribution block and pushing fluid back up the line on the MC. I have had that happen when racing before, but at the calipers, and had the same 'one time soft/low' pedal. I just have to wonder if this is also putting a bit of positive pressure into the MC and causing the cover leakage. I'd like to ask if anyone has experienced something like this, or has any other ideas on this problem. Here is a pix of the distribution block and lines; it is about 2" from the closest point of the Spitfire headers' collector.