Upgrading from kelsey hayes to???

That would be ;
Mr. Captain Obvious ,to you, but, Ok since yur a newbe, I'll let your arrogance slide.
Back to business.

There is NOTHING wrong with the KH brakes.
I have been running them on all my Classic Mopars, semi-continuously, since 1970. Including on one of the worst handling Mopar A-body combos of all time; the 70DartSwinger 340/4-speed on E70-14 Poly-glass tires.
That's 50 years; and during all those years, I have never had even one accident ever, attributable to braking. On the street, if you need more brakes, you don't really know how to drive, or your tires are junk, or yur just not paying attention. Don't blame the brakes. There is only one thing discs do better than drums; namely get rid of heat better. So they can take the abuse of multiple stops, in a short period of time ........ like in racing.

None of my KH calipers have ever been sleeved, and I have been running the Silicon fluid since it came out.

On the street, in the back, once you re-engineer your proportioning for your tires, 10x2 drums are more than adequate, . I went heavy in the back, and change my rear shoes between two and three times as often as the front pads. Those 295s in the back are like throwing out a parachute.
But even with those big contact patches back there, when sliding sideways, the rear brakes can do exactly nothing but make it worse. So that's where over 50 years of driving experience comes in handy.

BTW I'm no purist
My 68 Barracuda was originally a /6-auto. Today, it has a 71 360 in it, with a 64/65 Commando 4-speed, a GVod and 3.55s from about 71, in a narrowed 70 housing. The heads are alloys from 1999,as is the intake. The 750DP is older than probably you are. The Distributor had beem cobble together from so many different year parts, even JohnnyCash couldn't make up a song about it. The headlights are halogen, in 70's tech reflectors, cuz IMO, there's nothing better.The front brake system came off a 70Duster, the steering off a 73, the suspension is PST with a big solid bar and 1.03 T-bars. The shockks ar ancient 3-way Munros. The 70 Duster also donated it's Rally Dash with it's 150mph Speed-O, and the Dashpad is from a 69 Barracuda. The buckets are from an old RX-7, The shifter is a 1971 Mr.Gasket Bang!
The rods are from a 318, the crank is 1971 the KB107s were new in 1999. The valve gear is circa the 70s, as is the front of the motor except the pump is a Milodon, like the pan, circa 2001. I think I installed the AirGap in about 2002. The camkit is a Hughes from 2004.
I finally deleted the horns cuz I kept wearing them out, and so I learned to drive in an area where there don't seem to be any driving rules. Which works both ways cuz I like to slide around corners and punch it over speed bumps, that tuner-cars are crabbing over. I drive my Barracuda on gravel too, and on dirt, including an occasional jump, now that I fabricated a belly-pan for it.
The only thing purist about me is that I have been married and faithful, since 1977. So bite your lips and suck back your talons.
I don't care what brakes you run or how many G-bills you shell out to get them fitted; as long as you run the same tires, your street stopping distance is not likely to change much if at all, unless it gets longer, cuz you locked 'em up worse, cuz your head was still grumbling.
I was trying to save you hassles, time, and money. But you turned it into an opportunity to grumble. Fair enough, the world is full of grumblers.
I apologize if I came across as grumbling, but these online forums and Facebook groups are infested with guys who go out of there way to add there stubborn 2 cents, when in reality these "newbie" and younger guys getting into your 50 year hobbies is what keeps it alive and keeps the demand for used parts and keeps alot of people in business, im 40 years old and out of let's say 20 of my close pals theres 2 of us that care about keeping these old cars alive and as the years click by less and less of the younger generation want to do anything other than play video games and drive a fuel efficient kia, so the reality to it is, newbies should be welcomed with open arms, since joining this page ive bought thousands of dollars worth of parts from many members here and will continue to, and im sure alot of the other young blood could say the same, so all im asking is lighten up and get used to guys who have no clue about the flux capacitor you have 4 of on your garage shelf and be helpful instead of "confused".