I can't get the darn thing to seal. It doesn't help that I destroyed my threads getting a snapped stud off of the rear manifold /crossover.

Ordered OEM bolts and a felpro donut gasket.

It still seems something is missing.

8 mm bolts/studs. Gasket. Heat shield.

Weren't there square nuts somewhere in the equation?

Weren't they welded to the rear flange?

Well they're gone now.