The 79-98 arms use 12mm hardware. The 99-04 arms use 14mm hardware. This means the thickness of the bolts is larger on the 99-04. Stores advertise that you can use either arm on any car as long as you can get hardware. This is partialy true. The upper torque box will accept any hardware. The lower torque box does not. I put 99-04 HPM Mega Bite Jr's on my 81 Mustang. I had to enlarge the hole on the lower torque box, then it went right through. So basically, I would not use older arms and bolts on the newer car, because you don't want any slop in the holes, because it will chew up the metal on the body.