Welcome to the site. As far as I've seen, your only option is custom built headers for a 440 in an early A. I'll be in your same boat here soon when I drop my engine in to start mocking up a set. I'm going to try to build some using 2" pipe while puting 2 pipes inside the frame rail on the drivers side and 3 inside the frame rail on the passenger side. As for the brakes, just look for a 73 and later A-body donor car with single piston, LBP, disc brakes. Make sure you get the UCAs, spindles, calipers, rotors, and proportioning valve; also the dual MC if you don't already have one or go for one of the later plastic ones, but you'll need an adapter plate if you go that direction. Good luck.