[wixthedog]

If you gravity bleed or pump bleed (very slowly!) the brakes you wont have an issue. If you go to bleed and push the pedal to hard the prop valve will do its job and close to one side. There is a small plastic tool that can be bought for cheap that replaces the sensor wire at the prop valve, this locks the spool in the center position. If I'm replacing lines and have some 30+ year calipers I would always choose to replace them (and the wheel cylinders) but that's me.

The way you did the rubber lines is by far the best method.