I just ordered a bunch of parts direct from Classic Performance Products. I got the 1.125" bore dual reservoir master, with a 8" booster
All of the "kits" found on line are for cars and 1/2 ton trucks, they have the smaller diameter MC. Your truck came from the factory with a 1.25" MC. If you use a MC with a smaller diameter you end up having to push the pedal further to the floor to move the needed amount of fluid to activate the brakes. This could be dangerous if you get low on fluid or out of adjustment due to normal wear! I've never done the conversion you're asking about on a big truck (only on 1/2 tons), but have always understood you need to match the MC bore sizes when doing it.
I like Jerry's idea of finding a motorhome as a donor and moving ALL of that brake system components onto your chassis...someone else has already done the engineering for you!
Be safe!
Mike B
