I have a set of “standard”(original style, raised std port) stage 6’s here that have that casting number.

The “part number” for them is P4529335.

Not including the Chapman stage 6’s, there are 4 different versions of the stage 6.

-Original stage 6(raised std port, straight plugs)
-MW stage 6 with angled plugs(raised MW port, small kidney shaped chamber, needs .485 offset intake rocker)
-MW stage 6 with straight plugs(MW raised port, std heart shaped chamber, straight plugs, .485 offset intake rocker)
-street stage 6(later called the aluminum commando head, non-raised std intake ports, straight plug)