I am going to stick my nose in here. I am not being critical here but this is my observation.
Why would someone buy after market kits for a truck that came stock with these parts. A 1970 truck is not that old, that most parts are not available at your local FLAPS. The other thing is there are still lots of these trucks in wreaking yards, even here in busy SOCAL, for brackets and such.
I do not remember if a 70 had a dual system, but if it didn't it wasn't long before GM had a dual system in a truck. In this case you would just buy the first year parts. They will bolt right up without much trouble.
Go to your local parts store and buy the stock parts over the counter. MC, Booster and stock P. valve.
Just my take on this situation.
Now if you had a 54 like I do, then you start assmebling the after market parts and reading lots of article and online tech article from the kit manufacturers.
I hope you get your braking problem worked out. To educate youself, go to the brake kit vendors; they will have tech articals to answer all of your questions.
