Help: 71Duster Drums to 68 Barracuda Disc

I didn't think the boosters were application specific that way. I think I have had a drum booster on my KHers. Might even still, not sure. I have awesome brakes.

If you're gonna run the 9 inchers out back, I (That's me personally) I wouldn't bother with a P-valve, especially if you run bigger-than-stock tires back there.
I have a Dual M/C with a 15/16 bore. I highly recommend it with the KHers. Excellent feel and very nice pedal travel.I run 10 x 2.5 brakes out back with 7/8 W/Cs and my P-valve is gutted; so no proportioning going on back there. This has worked very well for me,with 235s in front and 275s or bigger out back.

IMO you can,as in, it's possible, to run the Duster drum/drum M/C on your KHers. These pistons do not require a whole bunch of fluid like a big single piston job.Nor do they NORMALLY retract as far. It's a little tricky, with the small reservoir, to get the system bled without sucking air, and once everything is up and running, you just need to keep an eye on the fluid level a little more often until you get a sense of how fast your pads are wearing. Then, at pad replacement time, (5 years from now with street pads), you will have to suck most of the fluid out that you have been adding over the months and years, so that it doesn't all gush out when you push all 8 of those little pistons back in. So because of those reasons, it is usually way less hassle to just run the larger Disc reservoir. So while it's possible, it's not recommended.

If you are putting an SBM in there, you'll probably also want to upgrade the T-bars. Mine are 1.03s and they are not too big.And forget the factory alignment specs. If your UCA bushings need replacement, get the Problem-Solver offset ones and put them in to maximize Caster with about .5* neg. Camber. Toe can be stock.Set both sides the same. With soft bars, put your bodyweight worth of weight in your front seat, unless you run double most of the time, then put the same weight on the passenger side
After the alignment, do not mess with the ride height, cuz that will mess with the alignment angles.