Well first off you will need a new bolt face for that. A 220 Swift has a much smaller bolt face than any magnum cartridge.
As far as the rest of the questions go, I would ask whatever gunsmith you are planning on doing your build, unless you want to do it yourself. There are dozens upon dozens of different kinds of stocks and chassis out there for Savages, so figure out what you like and go from there. Find someone who has some different stocks and see which one feels right in your hands.
For those calibers, get a heavy contour barrel (I would go at least varmint/sendero) and 24"-28". Any longer is really just extra weight.
For triggers, just read some reviews and try one out, you can always change it out down the road. I have 1.5# Timney triggers in almost all of my guns, but that's just my preference.
And out of curiosity, was your 220 Swift built on a long action? I always thought that was a short action cartridge.