CPP makes a power steering kit. Some have had issues with not getting power to the steering when standing still. That kind of defeats the purpose of power steering since that is when you need it the most. With a good front end you really don't need it when rolling.

Power brakes were an option in 1970 and there are at least 2 companies that make a disc brake swap kit. People have also added boosters from other vehicles.

A frame splice with a 72-93 truck might be easier than a whole frame swap. The frames are nearly the same height and width under the cab so that is where the splice is easiest. The rear portion of a newer frame has a higher kick up over the rear axle so either you need to lift the whole body, cut the bed floor or modify the frame.