Rear disc brake conversion was the first upgrade I performed on my M1028 and it probably was the best money spent. My truck came from a sandy area and the rear drums were scarred beyond turning. New drums and all the stuff that goes with them was projected to cost over $700, so I purchased a kit from TSM Manufacturing in Castle Rock, CO for about the same price. Installation was easy, and now the truck will stop on a dime going forward or backward. There's no grabbing after fording a creek either. You can read my thread at http://www.steelsoldiers.com/showthread.php?52121-Rear-Disc-Brakes&highlight . Regarding the emergency brake issue, the kit came with rebuilt calipers from a 1977 Cadillac El Dorado with the emergency brake levers built in. Remember to make sure the rear proportioning valve is adjusted properly and the sysem is full of the correct fluid.
Hope this helps.