The corvette kits work well, amazing the difference. I always end up fiddling a bit to get the centering adjustment correct. Lube definitely helps on the ball stud.
New steering systems don't really cost much and with age, they probably could use a refresh also. and eliminate the NLA cable issue plus get that like new feeling from the steering.
https://www.mrcool.us/fresh-water-cooling-kits.html Give these guys a call, I installed one of there kits on a similar vintage 350. They have great customer service.
21ft Thompson, strip to bare hull, Complete rebuild with a few modifications. Complete overhaul of all mechanicals and complete rewire. Pretty big project.