Parts from Japan?

There are a few places that deal with parts shipped in from Japan. The story is that the Japanese cannot keep their cars over 50K miles because of very strict emissions laws. I don't know if this is true, but there are a few US used parts dealers that say they only bring in parts from Japan...low milege cars. I did buy an engine from ASAP motors and was quite happy with it. Midwest Engines is another outfit that supposedly has a very good rep. A Japanese Engines is another one, although I've heard mixed reviews. Anyone had any experience with these places for engines or trannies? Thanks.