A further consideration is that you may already have a prop valve incorporated in your combination valve. If they car came from the factory with front disc and rear drum, and the car has the factory combo valve, then it's possible a prop valve is already installed.
Which you should correct before you start bending on those shiney new lines. If your car came with disc/drum proportioning valve you need to get a drum/drum distribution block which has a different hard line routing and may acount for why your custom lines don't fit. I know Dr.Diff sells them, I'm sure there are other sources as well.
