These pictures show the basic traveler set up on the 6000 series Lido 14. Schock sells a replacement line which is (I think) 5.5 feet in length. When I replaced mine (they tend to get worn at the hole in the deck) I just used the original line to measure a like amount of new line. It's 3/8ths diameter. First I tied the loop in the middle, fed one end into the hole in the gunwale and put a knot on the end to hold it so that the loop was in the right place. Finished by tying off the other end and trimming the excess line off each end.
The top of the loop, when pulled up at center can be no more than 22" from the bottom of the transom at center line. This rule is to prevent the traveler line from allowing the sail to be trimmed to weather of center line which might give an advantage.
The mainsheet end is split and spliced to a shackle which is used to attach it to the Crosby traveler. I hope these pics help you visualize it.
Check with the Lido 14 Association. I'm sure there is someone out there who has switched their classic to the Crosby style traveler and can help you find the best way to go about it. Good luck.
PS: I just found this picture of a newly replaced classic transom with a traveler system mounted right on the transom. The top loop of the traveler is hanging down in the boat in this pic. The picture is from the transom rebuild instruction article by DoubleWave. The article is part of the "Lidopedia" linked in the right column of this blog.
Until next, sweet sailing.