First, I would say: "Alright! I've got a 55 Columbia!"
I would take it apart, clean and lube everything, including the 2 speed hub. If it was used in 2nd gear all of the time as an exercise bike, I'll bet it's in good shape. Here's a webpage on the 2 speed Bendix hubs:
http://www.trfindley.com/pgbndxhbs.html
Then I would try to find the right shifter and cable for the two speed. That is probably the original hub for that bike, as the kickbacks came out a few years later.
Next the tires and tubes would be gently taken off, saved or sold, and replaced with some high pressure 26 x 1.75 or 1.50 tires on those same rims. This bike will fly in 2nd gear with good rolling tires.
Then some flat handlebars for a racer look.
If the repaint can be removed, you probably have good original paint. I'll bet the whole bike was red, but the best way to tell is when you pull the forks to clean and lube the headset bearings. The fork tube will show the original color. If that repaint comes off easily somehow, I would try to get it all back to 1955, except for the other changes I mentioned above. I don't think the handlebars or handlebar stem is Columbia so it won't be perfectly original. If the paint isn't usable, paint it any color you like or leave it as is.
Whatever you do, you should have a thread on it to show us what you do with it.