Ditto Ditto Ditto (search out 'Mr. Slimeball' for details).
As for dials, hands and casebacks, unfortunately, after the movement, those are the most costly components. If you have the cash, only a gen dial would do. If you spend alot on an aftermarket dial, eventually, you will end up having wasted that money when you end up biting the bullet & replacing it with a gen (by which time will cost 200% more than it will cost today).
Same with hands, which can often be found on ebay or the vintagerolexforum sales pages.
For a caseback, due to the scarcity/cost of a gen, I think your best bet is simply to purchase a good rep with a caseback that is made to gen specs. Alternatively, you can try either Phong or Yuki, because they used to offer gen-sized backs. However, be prepared to pay handsomely for them. For that reason, especially since a Sub caseback is a plain-Jane affair that is very difficult to ID on an otherwise gen-looking watch, I think the rep caseback is the way to go.