Even if you switch to 15" Magnum 500's, you may still need to take a disc grinder to the outside edge of the caliper for clearance. Also, watch out for the welding bead on the Magnum 500's; it may be a little bulky in for spots where the bead starts and stops. I had to take Dremel stone to the high spots.
One thing that is not mentioned in the instructions is the unique technique to bleed the rear calipers. Because of the slight angle of the mounting bracket, the calipers will capture a small air pocket at the top of the chamber when bleeding. To deal with this, you will have to pull the top slide bolt and angle the caliper back when bleeding. Do not remove the caliper, just tilt it back.
Installing this kit is very easy and includes three sets of spacers to center the caliper on the rotor. Don't forget to use the spacers when you torque down the axle flange or you may bend the caliper mounting bracket. Guess how I thought to mention that. You will also have to have tools to shorten your hardlines and WELD a brakeline bracket to the axle housing. It includes parking brake cables which you will have to figure out a way to connect to your year's system. I got my stock cables to fit the calipers. THE KIT WILL NOT FIT THE 14" MUSTANG STYLE STEEL WHEELS. I had to switch to 15" wheels and tires.
This is a cheap way to go disc brakes if you like/have time to spend modifying your existing brake cables to fit the kit. The kit includes two new brake cables of the same length, which my stang has a long and short cable. The instructions state they have other cables for sale......which doesn't make sense because they should've included it in the first place. You can use your original brake cables if you remove the tension spring. (time consuming)