Cold set frame or spacers?

cold set, but not how Sheldon advice, there is abetter method.
you will need a "thing" that I don't know how is call, but describe, basically is a bar with threads all the way, like a big screw.

rik, essentially it's like a threaded bar with two nuts on each side to pull in the dropouts?

A big bolt with no head - it is called threaded rod, you can get it at places like Homebase. Good for things like pressing heasets in.