I'm building a 1968 40 and I have replaced the front axle with one from a 78 (Disc Brakes). I'm still a rookie and I'm not sure if I should keep the back setup with drums and get a proportioning valve to run it like stock? I did a SOA and I'm going to run 35's. I put in a 350 with a Dana 20 Transfer Case and a T-18 4 speed. Is it more cost effective to convert the rear to disc or run the mix of disc up front & drum in the back? If I keep the mix is it hard to find the proportioning valve? I'm also in need of a Brake Master, I think the booster I have will work. Looking for ideas??? Thanks!