so see the differance look at the stamp on the tranny housing, b18c = JDM GSR, b18c1 = USDM GSR. If the jdm gsr is cheaper and has less miles and has a lsd then why the hells not ? The JDM one makes about 10 more power anyway. If you are tearing it down usdm VS JDM is really not an issue. even if you werent rebuilding it I wouldnt wory, I dont think ive ever seen GSr aftermarket parts usdm or JDM specific, they're really the same engine except for slightly higher comp pistons, and maybe a few other very very small insignificant things. I just got a JDM gsr from hmotors with 37K miles with LSD for 3300 shipped. Bottom line is to go JDM, its cheaper and a better engine.