That's a great idea WD!
Here's a couple to get us started... I have either bought from or worked very closely with both companies so I can speak for their quality, trust, etc...
DDX (Drag Drift Autox). Talk to Luis..
http://www.dragdriftautox.com Luis is really an expert. He really took good care of me with installation and standing behind it after the fact. (Vududoc here on NICO)
Automotive Advantage
http://www.automotive-advantage.comTalk to Garrett Hoboy. They have some of the best quality engines you can get... all from wholesale running auction cars... no junkyards!
Of course everyone knows about Venus as well.
http://www.venus-auto.com/ I think they have a reputation for low prices... I have heard mostly good things about service. I would guess they sell the largest volume of JDM engines here in the US.