I think you'll find a few different tubing types.

The classic Schwinn Varsity or Collegiate bikes may have "High Carbon" or "High Tensile" steel straight tubing.
Many Univegas may have chromoly steel, perhaps straight tubing.
Your high-end road bikes will have Reynolds 531 of Columbus double butted tubing.
And, of course, even within Columbus tubing or Reynolds tubing, there is quite a variety.

Assuming you do decide to have the dropouts replaced with track ends, I'd anticipate doing a full respray, although you might get away with repainting part of the rear triangle with a contrasting color. However, if you do decide to repaint the whole frame, then the difference in prep work between the nicest of the frames such as the Death-Fork Lambert and the cruddiest of frames such as the Torelli is likely minimal. In fact the powder coating on the black Schwinn might be more of a pain than the other frames.

You may find a top of the line frame for $100 which you'll then choose to chop up, but don't hold your breath for it to come up quickly.

From time to time frames with broken dropouts show up on E-Bay. Since you're wishing to replace the dropouts, why not start with one that is already broken. Anyway, just keep your eye out for one to show up.