If you drive a lot the springs hold dirt and water and road salt.
Other than that they may be for vibration from the rear end I guess, or maybe rock guards.....
I bent the smaller U shaped rear one from off the shelf 3/16" tube 18" or 24" don't remember, and it worked just fine without the springs.
The long line from the rear end fitting up to the prop. valve comes bent in half and you simply unbend it in one or two places and install it.
Mine is on one of the cars now.
The lines are usually sized to the system vacuum, power master etc. and of course disk or drum.
Within each category I guess the size of the pistons and volume of fluid needed would determine the size.
I have one car with stock drums and one car with Baer discs and still use the same 3/16" line out back.
I'd consult the caliper maker for the proper feed lines with your setup to make sure.
Then again the fitting on the rubber line if it came with them would dictate what to use too.