I'll be happy to answer any and all of your questions.
My '68 is the second generation Barracuda. First is the '64-66. The chassis is narrower on the first gen.
I have a customer with a '66. It's coming in the shop next week to have a few things gone over, including the brakes. I'll take some pics and see about posting them.
FYI, the '66 still had the single master cylinder for the brakes. If going to disks, you'll need to re-plumb the lines and use a later dual master.
All of the A-bodies (until '73) had what's referred to as the small bolt pattern (SBP)wheels. They use a 5 x 4.0" bolt pattern. The aftermarket used to refer to it as the BVD pattern. Not some weird underwear reference, but for Barracuda Valiant Dart.
If you want to keep the car with the small bolt pattern, the disk brake choices are more difficult. The first is to round up the factory Kelsey Hayes disk brakes. You would need the spindles and everything out from there. Not the easiest to come by, and out of production by the end of '72. Would need to find a donor BVD car with all the pieces, or hit the swap meets.
There are some aftermarket options. An outfit called Scarebird makes some adapters to use a FWD GM caliper on the stock drum spindles. I can't remember what they are using for the hub, possibly the one from the drum. I have a buddy running this combo on a '64 Dart. I can get the scoop from him.
Wilwood has rotor hats with both bolt patterns, but no off the shelf kit for the drum spindles. I'm looking into a combo using their parts for a customer for his Duster. He wants to keep the reproduction 15" SBP Rallye wheels that are on the car now, but go with disks behind them.
If you aren't married to the small bolt pattern wheels, there are options to swap the later A-body ('73-76) spindles into the earlier cars. The '73-76 disk brake A's used the same 4.5" bolt pattern wheel as the mid and full sixe Mopars of the era, along with Ford and AMC.
The most common BBP swap is to grab the upper control arms and spindles from a donor '73-76 A. The upper ball joint is larger on the BBP disk cars. There is a guy offering a sleeve to swap the later spindle into the small ball joint. I haven't use it yet, but he has an excellent reputation for his products.
On the electronic ignition there are a couple options. If the current distributor is good, I like using the Pertronix modules to replace the points. I prefer the Ignitor II for the circuit protection built in. I've installed a few, and converted my '68 over to their billet aluminum distributor.
The old junkyard swap was to grab a distributor out of a '73-up car or truck that was using the Mopar ignition module. The module will be on the firewall and the distributor has vacuum advance. If the module is on the air cleaner and no vac advance on the dizzy, walk away. It's a lean burn car.
You'll need the distributor, harness, ballast resistor, and module for the swap. Mopar Performance used to have it as a kit, but it isn't currently available like that. The components are available, and the current distributor is made by Mallory.
I have had mixed luck with the MP "Orange" ignition modules in the last several years. The quality isn't the same as it was 15 years ago. I've had very good luck with the Standard LX101 module.
OK, I rambled on enough for now. I'll be glad to crank out any info you might need.