Main brake line size
 

I have a 1990 454 SS truck. I have replaced my back brake lines from the axle tee to both rear disc with stainless steel lines I want to start slowly moving my way forward. I have heard the line that goes from tee rear axle tee to the proportion valve is 1/4 and some say 3/16. Has any rewho had replaced this line know what size it is. I was also needing to know what size inverted double flare for the inlet tee is on the rear axle and also what size double inverted thread the line coming out the rear proportion/combo valve. I removed the abs set up and put the line that was hook up to the abs dump valve directly to the proportion valve. Its been so long since I did this ,I lost the notes I took that told me sizes Of everything. Also heard that the factory put in a union about a foot after the line that comes out of the proportion valve to the rear brakes. See pic