my brakes are pretty much done for. i rebuilt the front calipers about a year and a half ago and i rebuilt the rear drums about 5 months ago. the parking brake barely holds even after adjustment and the brakes feel spongy even after bleeding. i want to do a disk brake swap in the rear but no one seems to know if there are ready made brackets that will fit a dually though. i'd like to replace the brake lines and put line locks on as an extra parking brake. as for the real parking brake i'm thinking about using a driveline brake. i'd like to put some sort of parking pawl on as a positive stop but i'm not sure how. one problem is the proportioning valve. all the electronics are gone and the tone ring in the rear diff wasn't there when i got it. it's my understanding that the proportioning valve on the late 80's early 90's f350s were tied into the abs and i do see wires coming out of it. also how do these work with disk brake set ups? i'd like to find a way to use either a load sensing proportioning valve or rear abs so that the rear axle can do as much work as possible without locking up. even though the rear end doesnt have the tone ring i have an autometer sender unit for my speedometer. i thought about a regular adjustable proportioning valve but then i'd have to test it under different loads to figure out the setting for each load and one size doesn't fit all. this is my trail/tow/daily driver/work truck so i want brakes that work good