The pedal linkage is different - the PB linkage has less mechanical advantage. The manual linkage with a power booster woul be real touchy.

I'm not sure if there is a plate change.

The drum/drum boosters are still available reman from your local parts store at reasonable cost. Masters are available also... but reman masters seem to be hit and miss on quality.

I bought a '70 Challenger with the factory drum PB setup. It was easy stopping with 4 "self energized" drum brakes and a booster. Not the most even left to right though. I didn't try repeated high speed stops until I upgraded to disks in the front. Personaly, if I was going to tear into it enough to put the booster in I'd go ahead and put front disks also. Its a big improvement.

An easy - but not cheap - way to make the switch is to call Master Power Brakes or look at their website. They seem to specialize in PB upgrades to MB cars.