awesome thankyou.In 66 they had Budd disc brakes as an option and it uses a balljoint made from unobtanium. 65-73 uses the same balljoint UNLESS it is a 66-68 Budd disc car.
If you are Googling balljoints for your Monaco, that is why it shows 2 different parts. If you check for say a 70 Monaco, it should show the same part# for disc or drum.
Kevin