Power disc brake upgrade questions (Bendix to newer style)

[jgbailey57]

I've already used the search function and found a lot of good info but I didn't find exactly what I was looking for.  My car is a 69 Charger R/T with the Bendix 4 piston power brakes.  The lines coming from the master cylinder exit on the fender side and the lid is the bolted style.  I'd like to keep everything under the hood as stock appearing as possible.  I know the booster is shot and needs rebuilt, the master cylinder probably needs rebuilt also.  I think that's my only option to keep everything looking correct.  I want to upgrade the calipers to the single piston style, probably the slider type because it's easier to find.  I think I'll also go with the taller spindles for the same reason.  I want the calipers to be rear mounted to avoid sway bar conflicts.  I have 14" slots on it right now but will probably run 15" steelies.  I'll probably go with the smaller size rotors so I can run 14's if I want, from what I read they are plenty capable of stopping the car safely.  It will get lots of street use and the occasional drag race.  It has a hitch on it and I plan to pull a pop-up camper.
Now for the questions.  Is it required to change the spindles?  Can I use the bendix booster and master cylinder with the single piston calipers or do I need to upgrade those also?  If i decide to temporarily use a used booster and master cylinder, what are my options with the least amount of work and cost?  What do I do with my old set up, sell it or stick it on a shelf?

[Ghoste]

You need to change the spindles because the rotors are also unobtainable and will need to be changed.  I think (think) the booster and mc are okay.
If the old stuff is okay and you don't anticipate going back to it, sell it off.  There are still a few old diehards like me running the four piston  stuff.

[BrianShaughnessy]

Camper AND small brakes        I'd be looking to go bigger.   Screw the 14's.

[Lord Warlock]

If you upgrade the brakes, the kit includes new spindles, rotors and calipers.  I've got a kit designed to replace the spindles, calipers and rotors only, and leave the existing master cylinder.  (mine was replaced shortly before I stopped driving it).  I recently found a shop that is rebuilding my original calipers so may be offering my brake kit for sale in the future.  Everything is still in the original boxes and plastic bags.