There are several options for rebuilds. Steer & Gear and Firm Feel are 2 companies that have good reputations and come up often. They can do stock rebuilds or tune them up for a firmer and more direct feel. I think rebuilds are in the $400 range and usually have a bit of a wait, I think I waited 2-3 mos when I had mine done.
Borgeson makes a good unit. I have one in the car but don't have it fully put back together, so no personal experience beyond saying they are smaller and weigh quite a bit less than the OE.
Power steering box takes a shorter column than manual because of bulk of the box. Column adapters are available to convert to manual box and still use the original power column. To go the other way, converting manual to power usually entails changing the column to a shorter power column.Is there a length difference power vs manual steering shaft 63-64 Plymouth? Thanks!