Ok I just bout a truck an 89 gmc Sierra and the guy didn't know what type of engine was in it all he could tell me was the fuel injected motor that was in it shot so he got it replaced and put a 350 edlebrook carborator. Ok we'll my actual question is how do I actually tell what kinda motor the guy had put in it

I would try to find out who (what shop) replaced the engine. The previous owner should have a receipt with some info on it. Get anything you can. go to the shop, have them look at their records or at least look at the engine. It's got to be a GM V8 of some type - probably from a truck. Go to other shops and junk yards and ask them to identify it. Take a few pictures of the engine and post it here. Maybe someone will recognize what it is. --- No one here can tell you for sure from your description. The carborator size would be a clue to the size.

It is a four barrel carborator I was goin to take it to a two barrel to save a little gas but I need to find out the year make and model it came out of

The make and model might not be an issue because the intake was changed. Try disconnecting the linkage to the back two barrels and save yourself the price of a new carb. If it lacks power, reconnect them. Take digital pictures first and keep the hardware in a safe place. You may not be able to buy the correct linkage if you lose them.

It lacks power now

The harmonic balancer on a 350 is thin. Probably 11/2 inch wide where a 305 is probably 2 1/2 inches wide. You could also run numbers lack of power could be from timing