A-body Cars w/ 383 & 440 Engines - Power Steering & Brakes

for brakes you could always use a remote servo like this Compact Dual Circuit Remote Brake Servo from Car Builder
or this Medium Dual Circuit Remote Vacuum Brake Servo from Car Builder
and had you considered electric power steering along these lines Convert Your Classic to Electric Power Assist Steering | eBay Motors Blog
they must be available your side of the pond.
neil.