Mopar virgin checking in with new 1969 Barracuda - with questions.... ;)

Greetings, friends!! It's spring here behind the Iron Curtain and I had a chance a couple weeks ago to drive and show the fish at a local car show!! I'm so excited that I decided all those years ago to go Mopar and this is a very fun and really beautiful car! I'm looking forward to making some upgrades to make it even more fun and safe. Specifically, I'd like to do a disk brake upgrade. I have manual drum brakes, and of course, small bolt pattern. I understand that the factory offered a 4-piston Kelsey Hayes system. Is this a better system or more effective system than the later 2-piston design? I do not necessarily need to keep the small bolt pattern, as I'm interested in upgrading the rear axle anyhow. What else do I need to make this conversion? Would I absolutely need a new brake master cylinder if I decide to stay with manual brakes? This is the car that I'd like to invest more in to make safer and faster (as inexpensively as possible). It looks like I'm becoming a real Mopar nut. ;) Please forgive me. LOL

By the way, this past winter I replaced the carburetor and now the engine really runs great!! What a difference. I suppose the old carb was just worn out; I haven't taken it down to see what the problem was, but now it's really responsive.

Enjoy the pictures of this nice family-oriented show.
Rebel Rides Behind the Iron Curtain: Rebel Rides takes part in Piaseczno's Second Classic Car Meet, April 16, 2016