In all my research so far, I haven't seen this one answered, so apologies if it's dumb. Is the plug for the engine harness to the ECU the same between 300 and 400 cars? For example, if you plugged the engine harness on a 2JZGE into the plug on an SC400 and had a 2JZ ECU in place of the 1UZ ECU, would it work? I don't know if there are any intermediate harnesses or anything between the engine and ECU, like if the body harness is interlocked somehow.

Basically I'm kicking around the idea of doing an NA-T swap into my 400, so if swapping in the 2JZ engine harness and ECU would make that part functionally identical to an SC300 then all the usual other stuff should apply (TT ECU mod, etc).

Or maybe I'm missing something blatantly obvious lol

 

The ECU plugs themselves are the same but the pin / wiring configurations are different between a 2jzge (SC300) and 1uzfe (SC400) just because they are different engine . Thus the ECU are also different.