Power/Manual Brakes?

manual brakes with the KH front disks work just fine. personally i always pull the booster. i like the peddle feel better and one less place to get a vacume leak

I don't think you can go four wheel dics without going power but I might be wrong.
yes you can

...You will need a different mc when you convert to 4 wheel disc...
no you don't. you need to remove the residual valve from the disc/drum MC and you'll be happier with an adjustable portioning valve. the stock one won't have very good bias under hard braking. of course brake size, pad material, tires and suspension all affect how well it all works :yawinkle:

good luck