4 brl intake options

A 600 cfm carb is going to be way to big for a stock slant 6, even a fairly heavily modified one the 600 is going to be on the big. Also, its not as simple as just rejetting, the throttle reponse is going to be very poor and the driveability will be seriousle impacted.

A Holley 390 is about the perfect size 4bbl for a \6 for stock to mildly modified.

There were two different 2bbl manifolds from the factory. One was a two piece welded aluminum piece that had a lot of porosity issues and should be avoided. Then there is the 2bbl cast itorn piece that is the one you want if sticking with factory parts. Mopar Performance had a M1 2bbl cast aluminum intake that is no longer made but may be found on ebay or a swap meet. The Clifford can be either a 2bbl or 4bbl depending on which carb plate you put on it.

Note: only the factory intakes and the Offy 4bbl intake can be used with a stock exhaust manifold. The others don't have provisions to seal the exhaust mainfold to the bottom of them. With those you will need to use headers or two Dutra Dual manifolds.