70 Duster power to manual brake conversion

OK, so a bit off the original topic, but I've been trying to get my brakes to a safe level and I've reached my sanity point. I'm still plagued by too little pressure to stop the car safely. The front drums were replaced with an SSB disc kit (and the spindles upgraded to be able to do so). The rear is an 8.75 stock a-body length with 10" drums. The rear cylinders were replaced with 7/8 bore just yesterday because I thought the cylinders were leaking. If I clamp the flex hose feeding the rear I get a good solid pedal. I haven't tried driving it like that though so I'm not 100% sure it's solid enough to guarantee the problem is in the rear. When I drive it it will stop it at a slow speed, and I can feel the front working. I've verified the rear drums are adjusted just to the point of almost not being able to get the drums off, and then backed off a few clicks. Strangely, it stops a little better going in reverse. The new rear cylinders made some improvement but not enough. I also put UV dye in the system since I was going crazy trying to find what seems like a leak. I find no evidence of anything leaking. If it's leaking, it's leaking air and not fluid, or it's hidden. I've had the drums off a few times just to verify everything. The pedal push rod when released comes back just enough to be hovering just before pushing in the master. It has plenty of pedal, but just doesn't have the braking power behind it.Every line is new within the last year. I've checked for the UV dye leaks at every point in the system. This power to manual conversion was mainly one of my attempts to fix this, since I thought the booster might be bad. I've had the front wheels off just to look at the front discs and verify everything, and it all looks snug and straight. If anything the pads are too tight against the rotors, because they are slightly touching when I turn the rotor by hand. I hope the SSB kit isn't this bad that I threw away $600 for it, and countless dollars and hours trying to get it to stop.