Thermoquad base gasket leak

So I bought a rebuilt Thermoquad 9000 series from a member here and installed with a Walker supplied thick base gasket. It's not sealing around the front drivers side corner and I'm afriad to tighten it any further. Any suggestions on what Thermoquad base gaskets seal the best? I see some available that have a nitrile coating.

This is a 73 340 with Weiand Action Plus 8007 spread bore intake.