I had three '55s and never did anything but add HD springs and really good shocks. I suspect that by today's standards the '55s didn't handle well, but it was fine for the time. If I was going to mess with the suspension, the first thing I would do is to replace the Hodaille rear shocks with modern Oleo-type units. Maybe you could find some brackets from a '56. I do know that the '56 torque tube and differential was different then a '55, but it is configured the same way and is dimensionally the same as a '55
Being a Century I am guessing that it has power steering? If so, you will have a bit of research to do if you want quicker steering. If it is not PS and you go to a quicker steering ratio you will need strong arms to steer the thing.