Which pump for 72 small sector 318

Here goes.
I want to convert from manual to power steering
I decided to cobble together factory stuff rather than opt for a full kit
Car is Stock 72 318
Stock exhaust manifoleds
Stock manual 24:1 alum box right now with small sector
Aluminim water pump.
I got the column length covered
Im going with a rock auto box from bbb.
My question is
There are multiple pumps.
Trw/federal/saginaw
Does it matter what pump i use or does the pump only relate to the brackets and line configurations.
Thanks