I will be swapping an 89 tbi into my K20. I am going soon to get new exhaust, and the truck already has new headers. The exhaust shop has the boss to weld to the collector for the O2 sensor. Is the placement of the sensor critical? Also, my donor engine has a 1 wire sensor in the exhaust manifold. It has been brought to my attention that I will need a 3 wire sensor. Does anyone know what vehicle I should have the parts store look up so I can get a 3 wire sensor?