disc brake swap

[carboy400]

I thinking about putting disc brakes up front on my '68 swb. I already have the spindles out to the wheel bearing castle nut from a '70-'72 GMC. One catch is the doner truck was a 3/4 ton. I think(a.k.a. HOPE!!!!!!!!!!!) ball joints did not differ from a 1/2 ton to a 3/4 ton truck. I know that the 3/4 had thicker rotors but I believe that I will be O.K. because I got all the parts. I also have a plan for the difference in the stud holes. What I need to know is there a difference in the brake line diameter, master cylinder, and proportioning valve from the 3/4 ton to the 1/2 ton? I hope to do this very cheap!!!

P.S. it not that I'm cheap but I'm also tring to get the financial comitte (a.k.a. My wife) to spring for a big block I foolishly sold to a friend and a TH700-r4.