I recently discovered a neat trick to help form new hard brake lines. I am a huge fan of nickel copper tubing; it is very easy to form and lasts forever. I have found that it makes sense to leave a little more material on the end of the line when making flares, as the nickel copper compresses more than steel does.
When replacing a hard line with a new line, it is a lot easier to make all the turns and bends by zip tying the new line to the old one as you form it. Place several zip ties at the end, leaving enough room for the fittings, then add zip ties as twists and turns are formed. This method still leaves enough room to use tubing benders to form correct turns without pinching the line. When the new line is formed, just snip the zip ties off, add the fittings and make the flares on the ends. Your new line will match the length and shape of the old line.
Using this method, the new line should easily take the place of the old line and fit in the proper clamps and holders.