brake lines

I bought a 55 that already had a Nova subframe with disc brakes grafted to it. Also has an S-10 rear end with disc brakes. I want to run new brake lines all around. What size lines should I use. The 9"booster and m/c and prop valve are new. The car runs and drives fine but the brakes arent up to snuff.

Every Older GM car and truck I own and that in the double digits uses 1/4 inch line to rear axle and 3/16 to each front wheel from prop. valve.

"The car runs and drives fine but the brakes aren't up to snuff."
What leads you to think, that the lines are the cause of the brakes "not being up to snuff"?