Paul, click on the following hyperlink to go to the trailer sailor website at
http://trailersailor.com/. On the left hand side of the home page, click on the word "forums." They have a forum specifically for MacGregor/Venture. If you don't get a satisfactory response there, ask your question on the general forum.
Also, the trailer sailor site has a tool that can tell you what running
rigging you need. You type in the make and size of your boat, and it will tell you the size and length of running
rigging.
Steve