I have 97 k1500 pickup. The engine was shot so I found a Tahoe with a bad transmission but the same 350 vortec. I swapped the engines. it seems to run fine in park when I give it gas, but when I drive it around it acts like its only hitting on two cylinders. It acts like its running rich. The Tahoe only had two o2 sensors but the truck has duel exhaust and has two before the cadys and two after. That's about all I know. Thanks for any advice!
From what you’re described, it sounds like you have two different engine and harness problems. You may also have a problem with the new engine ignition not being compatible with the other engine. In order to get the car working properly it will require more work than just swapping out the engine.
You may have compatibility problems with the engine harness not being the same. Another possibility is that a component, like the crank or cam sensors, can be different depending on the vehicle. Take a look and see if they all match. Pay special attention to the sensor rings, make sure they are the same and undamaged.
If you want a second opinion on this, consider having the engine inspected by professional mechanic to diagnose your engine problem and ensure a clean installment.