I didn't abuse the 5 speed while it was in my possession. Of course I have no idea what its life was like before me. This happened after the clutch was fully engaged, just winding it out from 2000 RPM up to redline. It blew up around peak torque.

I haven't torn it apart but I'm guessing the teeth of 3rd gear sheared off.

Yeah, eBay, craigs, wherever. I have a contact in Canada that has sold me multiple EJ207s, transmissions, brembos, etc. over the years. The JDM V7-V9 and USDM 04-07 6 speeds have the proper vehicle speed sensor. That wasn't eliminated until 2008. I believe the factory five center differential piece is designed for earlier 6 speed transmissions, which should be fine because that's what I'm shooting for.