65 273 Intake manifold

Looks like I made a mistake buying the manifold. Its a running car with the original engine. Just wanted to get rid of the troublesome 2 barrel.

Maybe not as a previous owner could have had the engine or heads replaced. Can you attach a picture of the engine, maybe a close up of where the bolts attach the intake to the head? What is the casting number on the intake? That might point to what you have.