i have a '66/6 i want power brakes, and discs all the way around.
I have dual webers and dutra duals.
what master cylinders and boosters from other cars will be able to bolt up and work with my slant? what will i need to cut, drill, fabricate?
how can i hook up the vacuum to the booster from my dual webers?

what am i overlooking?

HELP HELP HELP.

caesar

You can use any booster assembly, bracketry, and MC from an A body. To get discs in the rear is going to need some creativity. Either you have to go to an 8 3/4" or 9 3/4" (aka dana 60) rear axle and buy one of the various kits (TSM engineering, willwood, MPBrakes, etc) or do some manufacturing of your own. As for the fronts, you can use either the factory option early (pre 73) 4 piston setup, or the 73+ setup. Check out this link for more info on front disc upgrades http://www.moparaction.com/Tech/archive/disc-main.html

Any specific reason you want power? With discs in the front these older mopars have plenty of stoping action. You can use various diameter MC bores to tailor pressure needed.

One thing you may be overlooking is the cost/benefit ratio of rear disc brakes. Unless you are road-racing your car, you just won't be able to tell the difference in braking performance, assuming your drums are now in good shape. I live in the Rockies and still wouldn't consider spending the money.
Something to consider.