I have been boning up on distribution blocks, and read FSM blurb on warning light switch resetting once it has been triggered. No one seems to carry or has in stock a replacement drum/drum block that factory used on my 1200B. I have been shopping for a like device used by one of the big three that may be retrofitted to my truck. There is a lot of front disk/rear drum units available which contain a pressure reducer for the rear drum circuit which won't work properly, and not many for drum/drum. My understanding is with drum/drum no fluid pressure altering between front and rear circuits needed, and in the early days duel circuit brake systems, 1967 to 1970 or so, most manufactures used the same drum/drum distribution block for front disk/ rear drum systems utilizing a separate pressure reducing device down rear line from the block before it splits feeding both rear cylinders. One block I located that may be compatible with my truck is what GM A bodies used 1968-1971 which most likely will need to be retro fit with one or more bushings to adapt IH's brake line fittings. The other route to take would be to refurbish what I have now by cleaning and fitting new "O" rings, which I probably can locate at an industrial supply store. One problem, my warning switch seems not to be working electrically, and I think the problem is its spring is degraded or the guts are stuck with gunk. There is no way to disassemble it. Has someone out there retrofit a distribution block that all HI brake lines will screw in without bushings, and if so where would one get said device? On the other hand , if I could locate a new replacement switch, rebuilding what I have would be possible.