Juro, one running line that has a 6 foot head is the Rio Striper Versi-Tip. This is an intermediate running line, the head is .058 necking down to .042. Factory loop, and the color is light blue. There is no color change on the head.
If you want to test drive this running line, I can send it to you, or I would think Simon Gawesworth could be persuaded to send it you since it would be in Rio's interest to have you experiment with it.