What size hardline for disc brakes up front?

[Harrison.]

I've done a little digging and have read that drum brake trucks have 1/4" line all around and disc brake trucks have 3/16" line up front and 1/4" out back. My truck is a 70 model that someone has put discs on up front but front lines go through a tee fitting from the MC to 3/16" line and then use adapters on the hoses to go from 7/16-24 flare fitting (for 1/4" tube) to a 3/8-24 (for 3/16" tube). I'm about to re-build my brake lines and trying to figure out which I should be using?