We here at the 816 bicycle collective (KCMO) had a very hard time dealing with theft and heard all the usual stories of bikes gettin stolen or sold or whatever. The conclusion we came to was enforce a very simple rule, if you are building a bike from scratch you A. have to buy a 5 dollar lock from us or B. show us a lock we deem suitable and physically bring it to our shop.

Sounds a little harsh but it cuts down on people taking advantage of a free resource.
As far as the u-locks, the best suggestion we could give would be buying chain and locks at the hardware store and sell them for cheap.