Duster Battery Tray

MegaParts has them listed up to 74. I wonder what the difference in the 75 is?
$30 + a few extra for a bracket isn't bad for new.
Battery Tray 1967-74 A-Body, Battery Trays/Braces/Hold Downs/Hardware, 187-BT1067 Reproduction, NOS and Used Mopar Muscle Car Parts