Steve,
www.billmitchellsvd.com has an a-arm conversion for the fox cars that has the brackets in the correct position. I don't know if he will sell just the brackets. Some of the F5 guys are just using the M11 spindles.With all the brake kits avaliable for those spindles ,that might be the cheap and easy way to go.but you will have to adjust the upper mounts to take into account the M11's lower overall spindle height.