has anybody built there own blower manifold

It will work as long as you have a common plenum feeding the a/f to all 8 intake runners. Machine away the dual quad pattern, exposing a common plenum and then weld a plate to your intake that has the blower bolt pattern.
Depending on what snout you have, lining up the drive belt can be achieved by carefull measuring and location of your plate you are welding in.
And the machining should make the surface parallel to the crank, some dual quad intakes have the carbs on a slight angle.
DLI had intakes for sb and bb Mopars.

DLI
Did anybody take over the operation or are they now out of business?