I've found that the 1233s are a tall gasket. The port openings are taller, but the overall height of the gasket is taller too. On my engine, they hit the valley pan gasket and didn't want to lay down. I had to trim the gasket back to fit properly. Of course I've got 670s millled about .020", RPM intake ports matched to the 1233s, block decked and valley pan modified to clear intake.
The RPM has more meat in the flange area than some iron intakes. There is also the risk of early intake/ later head exhaust crossover mismatch with the '72-newer heads. The correct gasket is required to seal it off.
Verify the gasket is laying flat on the head surface and the plastic bolt hole inserts are in place. You may need the standard (non RAIV) pontiac intake gasket correct for the heads you're using.
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I could explain all this to the girl at the parts store, but she'd probably call the asylum.
White '67 LeMans 407/TH350/Ford 3.89... RIP
Red '67 LeMans. 407/TH400/Ford 3.25
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