If you are going to use the 3.5 engine from a 2005 you will need the complete engine wiring harness & PCM from a 2005 model.
John, Thanks for the reply but the concern is I dont have the PCM or wiring and the apparently the way the TB is contolled by the pedals is drastically different. Being the core engine is basically the same 60degree V6, Same stroke (84MM) just different Bore, making it larger CID. I swapped all the electronics out but struggled with mid engine Crank position sensor. So I was trying to get more details on how this sensor is different between the two versions. The older 3100 uses a 7x configuration apparently. I have the engine apart and see the seven slots in the crankshaft wheel where the sensor runs. Is the 3500 similar or different. The sensor is shorter, indicating something is different :) I did swap the balancer out as the 3100 has the crank angle sensore as part of the balancer, but was not sure the slot position was the same on the crank, making sure it oriented correctly (TBD center is the same). I got a good deal on the engine and dont want to break it apart to investigate. the other difference is th location of the MAP sensor but I believe that is simple and would impact IDLE and driveability and will work on that one later, If can get it started. The other missing sensor if the OIL LEVEL sensor (3500 does not have one located in the pan like 3100) but from reading up it should not prevent starting, just light the dash light. Do you have links to details of the internal and electronic workings of the 3.5 / 3500.