Recommendation for power brake booster-M/C-proportioning or combo valve set-up

[ZippyZoo]

I am requesting recommendations for a reliable power brake booster, master cylinder, and a proportioning valve or preferably combo valve set-up that just works!  Looking for a slightly "heavier", more modern pedal feel than my recollection of the in-the-day Chrysler super-light power brake pedal feel.
 
1971 Challenger with "OEM style" disc/drum brakes (originally manual drums).

I have been fighting junk "new" parts store master cylinders and what seems to be an "over-aggressive" power booster.  The brake system has an extremely "light" pedal and brakes which do stop the car well. But the pedal easily slides to the floor with slight extra pressure after a stop.  I eventually took the car to a certified master mechanic who works on older cars; he suggested the DOT5 was a problem, changed that back to DOT3, installed another "new" master cylinder – brakes behave exactly as before.  He now believes both master cylinders were no-good.  He is no longer in the picture.  Master cylinder and brake system has been bled multiple times.

1971 Challenger with a mild 440 single 4-barrel automatic.  Vacuum runs 15 inches Hg at idle.  Brakes are "stock" parts store reman K-H calipers and new RockAuto wheel cylinders. 15" stock Rallye wheels.  Spindles and caliper brackets are from a 1973 Challenger.  Older OEM style reman single diaphram booster (NAPA) and a "new" Chinese "Rabestos" M/C (RockAuto) replaced with a "new" Chinese "Best Brakes" M/C (parts store) installed by the mechanic.  Both M/Cs provided the same symptoms.  The 1971 OEM distribution block/proportioning valve was cleaned and rebuilt using parts from Muscle Car Research.  The 1971 OEM metering valve was was inconsistently sticking closed and was replaced by a tee.  I could not unscrew the cap to rebuild it.  OEM pedal to booster under-dash linkage in place.

I have found a large variety of booster-M/C-valve kits and "conversion kits" out there from Wilwood to Summit, etc., and individual components from independent suppliers such as Roseville, etc., at significantly different price points and many targeting drum to disc conversions.  On this forum, I have read so many complaints of the inconsistent the quality of the reproduction "OEM style" distribution blocks and metering valves, I prefer to stay away from them.  I would like to stay with the existing "OEM style" front caliper and rear drum components at this time......

1) What systems have you found that work "out-of-the box" and provide a more modern, firm, solid pedal feel from a supplier that is supportive and reasonable to deal with?

2) Other thoughts and suggestions?

3) Should I go through the hassle, effort and expense to return the system to DOT5, reducing risk of paint damage in case of any leaks?  If so, what needs to be done to completely flush the lines (hard and soft), calipers, and wheel cylinders?

I GREATLY appreciate your expertise and insights. 
Thanks – Bill

[70 340 Fish]

I converted my 69 340 Dart from manual drums to OEM front discs and used an NOS 69 Dart disc/drum master cylinder, a Direct Connection adjustable proportioning valve (to replace the factory valve) and DOT 5 fluid. I originally intended to add a booster to it but ended up preferring the manual setup. It was much easier to hold at impending lockup once I dialed out enough of the rear brake. I am converting my 70 Cuda to 4 wheel discs, with 13" front rotors with 6 piston calipers and 12" rear rotors with 4 piston calipers. The master cylinder, adjustable proportioning valve, and all the components are from Baer.

[ec_co]

I just have it installed, zero miles, so just install experience with it so far. I went with the Dr Diff front disc conversion kit (he has 4 wheel too) as it's been recommended a lot. Easy install, easily replaceable parts in the future if needed and looks good.

https://www.doctordiff.com/