Using mustang rotors for 4.5" bc

Thank you all for this very informative thread (I've read through it all). I hope you don't mind my adding my 2 cents or perhaps redundant questions. I understand what the thread was initially about but many people have added or expounded on other possibilities, so I hope I'm not out of line.

I have a 69 Barracuda with manual drum brakes, and would like to upgrade to much better disk brakes. So, the question is, which avenue to pursue (at a reasonable cost). Since I do not have the factory KH system, I will need to invest in many new parts, and I'm aware of that. I'd like the best bang for the buck to significantly improve safety, because I suspect that eventually I will want to upgrade the factory 318 to considerably more HP (up to 500, for example). Thus I will need very good brakes. The stock brakes suck horribly for the stock 318. I might consider going with the stock 4-piston KH option but that would run me $1000. That would allow me to keep the stock small bolt pattern (14" wheels I have are small but I like the original turbine hubcaps on my car; nonetheless, I am seriously considering ditching all that to upgrade to big bolt pattern wheels so I can get better brakes). I do not believe that I need to keep the small bolt pattern, but if I go to the big bolt pattern, I will also have to modify the rear axle (drums) and get new wheels too. What are your opinions on maintaining the small bolt pattern and buying a stock set of KH brakes?

Since this thread has been primarily about changing to the larger bolt pattern, I'm almost convinced to do that because it will also afford me bigger and safer brakes. So is the newer (73-up) factory disk setup better than the older 4-piston KH setup? Some say the KH setup is better. If I have the stock manual drum setup all around, and have to make major investments in whatever I do, why wouldn't it be a simpler, more economical and better solution to go with the 73-up system? I have to change out so many parts anyway, why not go to the newer factory setup? What would y'all do or recommend in my situation? I understand that if I go with that 73-up system, I will also be able to add even larger rotors (11.75"?) at a later time and have the best stock system available, correct? This is the system I'm leaning towards, even if it means destroying the originality of my small bolt pattern wheels. I prefer the safety of much better disk brakes.

Thanks in advance for all the advice given so far, and all the future advice I will need to educate myself in the ways of Mopar (I'm a Mopar virgin; this is my first). :)