Heat crossover

I always block the crossover on a supercharged application.
Use the 1213 gaskets.
Make a SS plate slightly larger than the crossover port.
Cut a hole in the gasket, just big enough so the plate lays in there(like the runner/ water port) recessing the plate.
Lay the gasket on the head, put a dab of RTV to hold the plate in place as you install the manifold.
The SS plate can be up to .040, that will provide a flat surface for the manifold to lay flat on as the gasket is .060

Best of luck on your project Mate.
What size blower? 144/162?