do i really need 3" exhaust

1971 Dodge Demon 340 have original manifolds on it, the left side down pipe is 2 inches and it seems very titght around the clutch and starter in fact who ever had it before me looks like they had to smash and squeese around that area to make it work, the right side is 2.25. what is the original exhaust size that came with the 340 Demons?
Thank you.