Looking for master cylinder suggestions on somewhat unique setup

The more I look at my whole setup the more I debate updating my proportioning valve as well just to clean things up. I have no idea what it is actually off of and can't really seem to find a match for it. Need to see if I can find some part numbers on it I guess. The way it actually routes lines and stuff though isn't exactly ideal, so I wouldn't mind something cleaner. The car seems to stop well enough for what it is, so can't really complain there. As best I can tell from casting numbers the front brakes are something like 71 Challenger parts. Rears are something like a 10" drum, though the shoes are very slightly "different" in that they have square slots where the parking brake lever attaches. Tried buying shoes for something like a late 60s B body in the past when I replaced them and they had round cutouts there instead, so couldn't install the lever. Luckily the guy at the counter was actually a Mopar guy and we figured something out, but I should have written down what we actually found as I can't recall anymore.