Actually, there is only one ECU, which is the problem... you can't eliminate it without having problems with the gas gauge, speedo, and other dash gauges...

You will be in for a lot of custom wiring either way, some good searching on my.is and here will give you almost everything you need, but be prepared for a lot of custom wiring, even with your full swap...

 

The whole reason I want this is300 is because I already have the GTE non vvti motor . I was hoping it would be a drop in swap just like it is in the 2nd gen gs300's. Im trying to factor in the cost of the car and how much to do the swap. I can pick up this 2002 IS300 5sp MT with 103k miles for 4300, But it has a salvage flood title from NJ due to Super-storm Sandy. I just planned on using everything from my aristo to do the swap.
So couldn't I just run the Aristo GTE ECU, and wire in all the dash gauges like we have to do when we do a swap in a 240sx? My RHD 89 240sx coupe has an rb20 and i have to splice in the dash harness into the engine harness to get the gauges to work. Same concept?

 

Correct, the dash gauges are controlled on a serial bus, not analog like the old days...

It is possible to get some of the gauges to work, I don't remember which, but others will never work without the factory ECU in place... (and controlling them)

 

the IS bcm and ecm run off the same computer which is why its suh a pain to deal with our cars tuning ( from what I understand if im wrong feel free to correct me)

 

not so much tuning - that is because the computers are extremely smart and any changes you make externally result in the factory ECU trying to compensate for those changes...

but yes, they are the same computer...