Another noob question - JDM?

Okay, JDM stands for Japanese Domestic Market, got it. Which apparently means that it was a Japan-only feature, part or vehicle.

USD stands for United States Distribution, or something similar. Parts, etc., available in the States.

My question:

Most of the "JDM" (which I originally thought was a brand name, yep, noob here! I learned mechanics with 460 Ford engines wearing blowers and twin carbs, so turbos and AWD are still a bit new to me!) parts I find online are engines/transmissions or front clips. Where can I find other parts such as the wicked vented rear taillights on the '93 JDM GT4 (or whatever label it wears in Japan)? Can the local Toyota dealership order JDM parts?

Also, what were the differences (other than right-hand drive and the taillights) between the JDM and USD 90-93 ST185's? Pictures would be helpful and greatly appreciated.

Lets start from the end, what is the difference between JDM to USDM model (or any other region)...
Well, first of all there is a difference between the emission and pollution regulation which leads the manufacture to tune the engine and the systems around it differently.
Sometimes is only come out as unnecessary systems like the EGR and some time is even change the engine power limit.
Other differences you can find is for example between hot and cold regions.

Where do you get parts...
If you want new parts you can start at http://www.1sttoyotaparts.com/.
You can find here 90% of the USDM and JDM parts and if you know the original Toyota part number the search become much more easy.

ps. you can learn most of the shortcuts from here: http://www.gtfours.co.uk/what/abbrev/abbrev.htm

and welcome to the world of turbo boost and 4WD... ;-)

www.rhdjapan.com

you will find your tail lights in there.

As for ordering JDM parts from your local dealer... they may or may not choose to help you, and if they do, they will charge an arm and a leg for it.