O.K. gang here I go, i have read about 3 pages of this section. My situation is this, I have 4 wheel disk brakes on my 51 1/2 ton Chevy 3100. I purchased the disc/disc power brake master cylinder set up. Thought this would be pretty straight forward, i am mounting it under the cab in the normal position.1st question is there a specific size of brake line ?? I went to parts store and found out there are about 3 sizes?? Is there a certain size or does it matter?? i bought 3/16th's! Also proportioning valves? From what I have read I need this because of where the system is mounted? help please.