I had a friend that had similar issues when he redid the brakes on his 70 cuda. I am almost sure he could not get any fluid from the proportioning valve to the front brakes. As best I remember he had his lines on backwards to how they were actually supposed to be. I think he called either inline tube or fine lines whom ever he bought the kit from and they sent him the correct diagram and that fixed the problem.
He told me they went on backwards to how it appeared they would have.
That is just from what I remember from our conversation.
Hope it helps, Matt