Thank you only thing I can see is where you can tighten your steeringFollow the hoses from the steering box to the power steering pump. On most the reservoir is on the pump. Gauge is within the reservoir cap. Don't overfill, it will blow the excess out the cap and make a big mess.
Looks as if I do not have power steering but a close ratio box. I have taken out a lot of play but still annoying when driving wants to drift a lot.Can't always follow the hoses from the steering box, some motors have the pump in odd places, like other side of the motor, so the hoses get obfusticated in body panels etc. But can always look at the belts, there will be a pulley attached to the pump, with a belt on it somewhere, even if it's part of something else, like the alternator loop. I've yet to see any remotely close to stock setup use an electric power steering pump.
If you are running same size tires all around rotate front to rear and rear to front. If any improvement could just be tire wear. If still a problem and still drifting might be worn out tie rod ends, idler arm, or everything else considering a 72 front end. Power steering will not improve a bad front end problem. I will guess at this time that you need upper control arm bushings more than anything else. The upper control arm bushings control caster and if worn will cause the problems described. The tie rod ends would be my next suspect followed closely by the idler arm. Everything you describe points to a complete front end rebuild not a power steering upgrade even though that would make parking in tight spaces easier!