Wilwood rear disc brake conversion

Has anyone done this conversion? Wilwood kit#140-7144. I'm trying all the pieces and making sure the setup will work and ran into a problem that the wheel studs wont let the rotor sit flat against the axle.The shoulder is to center the drum,and I need it without the shoulder. I tried several places online to find something close,no-go. I tried calling Wilwood and they couldnt help and said to call ARP, I did and they would need to be special made. I dont want to have to drill the rotor out because if the kit doesnt work I can return it. Any sugestions would be appreciated.