The stem and bars look good to me. They suit the frame.

A new wheelset in 700c would be your best investment, beause as you state, they can go from frame to frame. The difference in spacing from 126 to 120 is not a concern. Tightening down the nuts will do that for you.

A tube of grease, some loose bearings and maybe some new brake rubber.

When rebuilding the bb and headset, take old bearings to your lbs. They will size them for you.

Job done.