Engine Probs?

guess i misrepresented the prob. I recently put this rebuilt 360 in my cuda. It was running great in the pick up i took it out of the pick up was wrecked. My problem is the engine is running really rough. The engine did sit for about 3 months before i got around to putting it in and starting it. Will that affect the carb if gas was still in it. The distributor was the one on the engine when i got it and it was timed perfect in the truck. The ecu was in the car when i got it 8 years ago and it was sitting outside all that time. The wiring is all original with exception of the electronic ignition wiring which was also in the car. Basically the engine is brand new from heads to pan. That is why i am confused. Maybe that is a little better info thanks