Can a 400BBM w/cheap aluminum heads compete/dominate against the street LS?

Agree, were sucking hind tit , compared to the availability of G M stuff, anybody can make a G M run !
I think Mopar does ok on engine options. It's body panels and support modules. You can literally build a 55-57 Chevy from all new parts. Ground up. Pretty much true for 66-70 Camaros and Chevelles.