I definitely would replace the upper control arms for improved caster. My 55 has tubular control arms. I'm not sure what brand. I would consider disc brakes while I was in there. They are all over Ebay. There has been a lot of discussion on trifive.com in the steering forum.
You didn't mention steering, but my 55 has a Borgeson/Delphi and I don't have the steering sorted out yet but I am not happy with the way mine drives. I am going to get the front end aligned when I get my wheels on it and if that doesn't work I will probably change to a CPP 500.
Wiring harness are a cheap investment and relatively easy to change.
When I had my Nomad, the front floors and cargo area were borderline rusty. Lots of pinholes. After dreading it for a long time I finally ordered the pans from CARS and once I got started, I actually enjoyed changing them. The cargo floor was interesting in that is adds so much structurally to the car.
Go to
http://www.trifive.com and it's just like this forum. Lots of info over there.