I'm back with my dual 3.5" speaker brackets
I have built three more speaker sets to fit in 6x9 spaces since I did my cars. One set went into an old Chev pickup and used Crucnch CRS40CX drivers and another into a Chebby coupe which used Kenwood KFC-1093PS drivers (with some cheapo 6" bass drivers under the back seat) if your looking for some 4" spaeker options. The third setup went into a nicely built Studebaker and it used Focal 100KRS fronts with some Focal Utopia BE13WS put into sealed enclosures that hid under the seat and it sounded awesome! Another option if you recently inherited a small fortune:-)
These 4" drivers should fit into '74Sports 6X9 panels if you orient them properly.