As others have mentioned, the coils are there to take up motion between the body and frame. Yes, you can get by without, just pay attention to the motion. See how in The Rocknrod and dracko's pictures the lines go way over toward the driver's side and come back? It spreads the motion out over a whole bunch of line. That is more or less what the coils do.
Here's a disc brake conversion done in the 80s:
