I am ordering all new lugs nuts and center caps for the draglites and i have a few questions to make sure i order the right parts..

1. When i measure for the center cap to get the diameter, do i measure teh OD on the cap or do i measure the inside? Or do i measure the OD of the lip at the bottom of them?

2. What size lug nuts do i need to buy? I have ones to fit the back but, they do not fit into the holes in the skinnys, they are too fat. But when i use the skinny ones i got they are a different thread pattern. They fit brians camaro and they fit my buddies third gen camaro, but will not match up with mine. But they are all 1/2in??