Detroit Muscle Technologies make a great resto kit. Not sure if he has the screws. He is a member here and also sells the kits on Ebay. If you do an EBay search for "DMT heater box" you will find his stuff. Good luck!
70 Road Runner 383-4 4 speed FJ5 & black guts 70 Charger R/T 440-4 4 speed FJ5 & white guts