Could you adapt the Chrysler setup from back then ? my 53 had a generator / power steering pump combo with a powered gear. worked good .
The 51-53 desotos have needle bearings as the top bushing of the kingpin. Bearings are hard to find, but are part number NB-15OH by Torrington. They should help reduce effort to turn stopped and at low speed. Swap the whole spindle on and gain 12" drums at the same time, or have your plymouth spindles machined to take them.