Back when on the nearby circle track,the guys who ran GM 6's used to invert the intake,cut out the bottom and all the dual walls for the intake heating passages.Make an adapter,block off the now on the bottom original carb port,good to go.The manifold is tilted the wrong way,but it worked ok.
I have enlarged the stock opening to an oval shape for a Holley 2300 two barrel,ya wind up breaking through into the area heated by the exhaust.I welded up the holes ,ground them smooth,added a home made carb mounting plate.It's not all that difficult to do with bachyard mechanic tools.Doesn't seem to be room to open the top for a 4bbl.It's my opinion ,390 Holley 4bbl is overkill for a street 235,you can get the same power with a Holley 350 CFM 2 bbl(a 350 2 bbl actually flows about 280 cfm when rated like a 4 bbl).And like I have said before,the Holley 350 will out perform and get the same fuel mileage as those butt ugly over rated Holley Webers.
