Cromor is butted Chrome-Molly tubing that is seamed (made from flat bar) rather than seamless tubing found in the more expensive steel tubesets. It should make for a stiff frame that is just somewhat heavier than the better steel frames of the day. I wouldnt get too focused on "restoring" the bike with a particular specification of vintage components. Such frames were often sold as bare frames for the owner to build up however they saw fit. A "restoration" with eithor Athena or Ultegra components is not such a notably collectible bike that it would really be worth any more than the sum of the components. If you actually intend to ride it (as opposed to just hang it on a wall and stare at it), I say just build it up with whatever decent quality components you want and can afford for it, and it is fine if they are somewhat newer.