"I'm not sure how good Yuki's cases are. check them out, ask around."
The two cases (5512/5513) I got from Yuki in May 2014 were as good as any I have seen. They are no longer shown on their website but a few other sellers will have similar cases. Read in the rolex section to see who has what.
As for 1520 parts...almost all the parts are the same for 1520, 1530, 1560, 1570 except for the escapement parts.
Escapement = balance wheel, hairspring, pallet fork, escape wheel, and a few others. Get a rolex parts list for 1530 base movements or for the 1520 and see what you need. The 1530 was the first of the series so all of the similar movements that followed are called 1530 base movements..
1530 base movements = all the movements above + date, day-date, anti-magnetic, and GMT models with the same 1530 base movement
If your balance wheel, hairspring etc is damaged, you will have to use 1520 replacement parts because although the main plates are similar you will can use only 1520 escapement parts.
1520 = non chronometer with flat hairspring
1570 = chronometer with Breguet (overcoil) hairspring
Learning about movements is slow, dull going but it can save you a lot of $$ and headaches.
The more you know, the less it will cost. Most of the time.
Learn all you can before jumping back into the project.
Believe it or not many RWG members worked on genuine name brand watches before getting into replicas and Frankensteins.
Why would anyone need a head start?
Because replicas and Frankensteins are harder to work with.