Your best bet is to do some footwork and find places local to you and check them out for yourself. I purchased my first JDM engine and thats the only way I was gonna do and Im glad I did. Many of the engines looked really beat up (cosmetically) and appear to be rusting or have lots of oxidation on them. Heres some things to look for:
1. Make sure the TB's move freely (if they are stuck there is or has been water in the plenum. It seems that many of these engines are sitting outside at some point somewhere, and get water in them. 2. Make sure the engine turns over and isn't "locked" 3. Check the oil in the drain pan (no chocolate milk looking oil!) 4. Look for signs of oil on the throttlebody inlets 5. Pull and check spark plugs. 6. MAKE SURE it comes with a warranty (30-180 days) and stay away from any place that doesn't offer one. No startup warrantys. Places with a good warranty usually sell good engines that have already been compression checked. You will pay more but you get what you pay for..