I have a 34 ford, bb chevy pro street with a 9" ford rear. I am presently lowering the vehicle, and while the rear end is out I am considering changing the back to disc brakes. I presently have mustang II disc brakes in front and 3/4 ton truck drum brakes on back. First, will I be gaining anything by changing over to rear disc brakes?. Next, I am confused on the bolt pattern on the axel plates. I had this rear end built using 31 spline, ( I snapped off three sets of 28 spline axels in one summer), and It has the large brgs, but the bolts for the backing plate are 3/8" and a 2" x 3 9/16" bolt pattern. Everything I see is either large or small brgs and the bolt patterns are different. I would appreciate any and all information and help on parts. thanks onebad34