Slipping a 130mm into a 126mm spaced frame is no problem with a steel frame. No bending -cold-setting- needed.
You can run any brand of freewheel with any brand of derailler. The only problem you may find is that short cage deraillers won't make the shift onto the larger sized cogs -- say 32-34 tooth.
I'm spinning an Atom freewheel now on my commuter with Suntour deraillers.
Keep looking. Check out this weekends garage sales. I often find 27" wheels.
Good luck.