TRied it...
That site is full of wrong stuff. Type in 68 Barracuda 340 rear wheel stud and it calls out a 1/2 -20... WTF?
DORMAN Part # 610103 {Click Info Link for Alternate/OEM Part Numbers} Serrated Stud; Thread; 1/2-20; Knurl Dia.: .673"; Length: 1-19/32"; Shoulder Length: 9/16"
Rear; w/Posi-Traction; Right Hand Thread
$0.89
DORMAN Part # 610186 {Click Info Link for Alternate/OEM Part Numbers} Serrated Stud; Thread; 7/16-20; Knurl Dia.: .472"; Length: 1-1/2"; Shoulder Length: 11/32"
Rear; wo/Posi-Traction; Right Hand Thread