Could use some help with power brake conversion for 1971

[57rookie]

So I have a very bone stock 1971 GMC survivor 1/2 ton. It has front disk/rear drum brakes from factory. It has the proportioning valve from factory.
What is the easiest bolt on solution for me to convert from manual brakes to Power brakes - simply put - who sells the best STOCK power booster conversion that would take the least amount of work to add Power brakes????
Many Many thanks to anyone that would take the time out of their day to reply to this question!!!!!!