There is not a readily available accurate rigging diagram for these ships. They are typically printed in 1/96 scale, so scanning one is a bit difficult! The easiest way to get one is to order one from the Smithsonian:
http://americanhistory.si.edu/csr/shipplan.htm
Their prices are reasonable, but it will take some time.
If you don’t want to go that route, here is a simplified explanation of the rigging. I don’t have diagrams for everything, so take a look at the photos at steelnavy.com and smmlonline.com for placement.
You should run two lines between the tops of the upper sections of the main and mizzen masts. One goes directly between them, and one goes via the triatic stay- the vertical shown to right of funnel in this photo:
http://www.steelnavy.com/images/liberty/ob10.jpg
The starboard line serves purely as a radio antenna, and should have a lead dropping down from it near the bridge. The line running from the main mast to the triatic stay also supports the signal flag halyards. There should be three of these near the flag bag on the bridge, and another two forward of no. 3 hatch.
Moving on to the cargo gear, there is a pretty good diagram in this document (see Figure 4-21):
http://compass.seacadets.org/pdf/nrtc/sn/14067_ch4.pdf
This diagram shows two different ways of rigging the topping lifts and guys. The standard way to rig guys on Liberty ship is using two guys per boom instead of using the schooner guy between the booms shown on the left (bottom as shown in the file) rig. Single topping lifts as shown in the left (bottom) rig were more common than the multiple topping lift.
This is how booms would be rigged when working cargo- when at sea they were secured. They could be lowered so they sat horizontally in cradles, or they could be raised vertically and secured in collars on the crosstrees. The lowering them is easier (you don’t need to have someone climb the mast to secure them), but it is not always possible if a deck cargo is carried. The trumpeter kit has cradles for the booms at no. 1, 2, and 5 hatches. At no. 3 and 4 hatches the boom cradles were located at the corners of the boat deck. In order to be secured in these cradles the booms at no. 3 hatch had to be crossed.
These ships also had heavy lift gear at no. 2 and 4 hatches. This diagram shows how they were rigged:
http://www.globalsecurity.org/military/library/policy/army/fm/55-17/ch3.htm#sec3-14
When the heavy lift gear was in use the other booms at that hatch had to be secured vertically.
The last item to include is the stays that support the masts. The mainmast has four, but the foremast and mizzenmast have an additional one running fore and aft opposite the heavy lift boom. The forward heavy lift gear is rated at 30 or 50 tons depending on the ship, so there are actually an additional two stays (for a total of seven). The final two extend forward and are secured near the rail alongside no. 1 hatch. These interfere with cargo operations at no. 1, so they would normally be draped down in front of the foremast and around to the sides of the mast house when the heavy lift gear is not in use.
Regards,
Chris Friedenbach
Crewmember, SS Jeremiah O’Brien