I think I'm just gonna go with this gasket:

Mopar Performance P4529455
Gaskets Head Composite "B/RB" Up To 4.42" Bore .038" Thick, and has the stainless fire ring.
$73.95 for the pair.

But Summit is showing out of stock on them and Jegs doesn't show them at all on their website, so now I gotta hunt these down.

1970 Challenger, all aluminum 528 Hemi, HDK suspension, Tremec 5 speed manual