[AZKen]

1. First thing is tell us what components you have. Compressor? Brackets? Pulleys? Condenser? evaporator? Dryer? Dash vent? Special heater box? Hoses? Many of these will be replaced with new but many are nice to have and we need to know what is there.
Report what parts you have, Study the internet to learn the names of each.

2. May be obvious but a 77 PS pump will handle a 77 box. Probably several years have the same system. Do you have any bracket for a PS pump? If not, you will have to buy or make. Most any PS pump would probably work. The pump does not care what it feeds.

3. Assume you have a stock 305 V6 motor? Factory dash A/C outlet, not a hangdown/underdash unit?

The issue with all this stuff is the mounting locations and bracketry.

Are the 1966 factory PS ram and steering arms to be used or 77 C10 components?