5/16 UNF Thread. Lever adaptor clevis bracket as used for many motorsports applications.
These are used to fit the pedal box to the floor pan. You will need to cut a 21mm hole in the floor pan insert the top hat and weld around the top.
Alloy 5/16” – 24 UNF Thread Male, St/St 8mm Diameter Ball - (Total Length Approx 45mm)
Alloy 5/16” – 24 UNF Thread Female, St/St 8mm Diameter Ball – (Total Length Approx 53mm)
Aluminium Twin Cable Accelerator Block With Lockable Grub Screw.