Red Head if you want to make sure the new (rebuilt) box doesn't have excessive slop. Worth the $$$. Just google Red Head Steering and you will find them.
The are available through most of the national carriers such as Oreilley's, Advanced, etc. Probably NAPA. I have heard Red Heads are the berries, but you do fork out a bunch for them. Mine from Oreilley's functioned without issue then I decided to replace with power steering. Got that from buyautoparts.com (I was leary) but so far so good on it.