My truck is 1 ton- 60/14b. 14b has disc brakes using D44 calipers. At first I did the swap and left the stock K5 master cylinder on there. It worked ok for awhile, although the pedal wasn't as firm as I thought it should be. Then after a couple weeks of sitting I noticed that rear resevoir on the master was empty- It had been leaking right from the master. So it was new master cylinder time. Went to get one and figured I'd upgrade to the 3/4 ton master. First off, the 3/4 ton master looks waaaay different that the K5 one. When I asked the parts guy for what I wanted, he asked if it was the JB6 or JB7 system. I didn't know, so I asked him to bring them both out. One had both resevoirs the same size, the other one, one was bigger than the other. The piston on the one with different sized resivoirs was bigger so thats the one I got. Can't remember if that was the JB6 or JB7 though. /forums/images/graemlins/thinking.gif Anyways, after wearing my arm out for half an hour bench bleedign the thing, I bolted it on, an oh man, what a HUGE difference! Pedal is solid as a rock and the truck stops as good, if not better, than my DD '94 F-250. I can leave skid marks with the 42's on command. So those that are running the 1/2 ton/K5 masters with the disc brake 14b, might wanna try upgrading to the 3/4 ton master. Made a big difference for me.