[toytruck]

Got to be the master cylinder. Did you bench bleed it before you put it on? Or the master cylinder bore is to big for your brakes. Is the push rod the right lenght? Or the fluid bowls are too small. Compare the mustang master with the new yorker. They need to be close to the same in fluid volume and bore size. But more volume and less bore is even better. Hope this will help to get you on the right track.