You should be able to swap everything straight over. My understanding is that you need a different master cylinder because there is a valve at the port that keeps residual pressure needed on drum brakes to keep the cups sealed in the wheel cylinder. You don't want this residual pressure on the discs because this and will cause your pads to always have pressure. The proportioning valve is different. You can just ad an inline adjustable valve in the line going to the rear drum brakes. I have my 69 Cuda almost done and it has front drum brakes which I will leave this as since it is a number matching car. My 67 notch back had 9 inch drums and I had found a 1967 formula S 273 with the 4 piston Caliper factory setup and swapped the entire suspension to my 67 that had 9 inch drums. I also swapped the rear diff with 10 inch drums. I drove this car without modification to the proportioning valve and it never seemed to have a problem stopping but that was years ago and I plan to install a new oem type proportioning valve. I have a book I found a few years ago entitled "Performance Handling for classic Mopars" by Tom Condran. "Updating Suspensions and brakes with Factory Parts and your own tools". I don't know if this is still available but it is GOOD. Explains everything including being careful because some suspension parts will bolt up but could change the steering Geometry. Published by Faster Forge & Press, San Bruno, CA additional copies ACME MAIL ORDER P.O. Box 282612, San Francisco CA 94128-2612. I highly recommend it. If you cant find a copy I can look up your questions. A little rusty on suspension, been years since I did my 67 front suspension which I am going to rebuild again, This time I am using the offset upper control arm bushings for increased Neg Camber for better handling along with polyurethane bushings. another note is you swap out the tie rods with the larger size. The taper is the same just the threaded ends are larger so you have to replace the sleeves. I will have to look at my parts or find it in the above book.
