You can use the 2.7 computer with the 3.2/3.5 conversion.I have done it this way with no check engine light on after hearing it run.Tha radatior is differant too.The 3.2/3.5 radatior has oil lines going to the radatior,The 3.2/3.5 throttle cable is longer and the heater hoses are differant too.I have ran into this too.If you replce the computer with a new one,you do not have to go to the dealer.The Mastertech scan tool from Vetronix will program and burn the vin in the new computer.Here is Vetronix's website,
www.vetronix.com