I think the plans in question may be the set drawn by Harold Underhill, which we've discussed in a couple of other threads of the Forum. Underhill was a fine draftsman and a genuine expert on the subject matter. Unfortunately, through no fault of his, those particular plans have gotten somewhat mis-labeled.
He drew them, I believe, in conjunction with the publication of his book, Sail Training and Cadet Ships. The plans were intended to represent the class of ships built by Germany in the 1930s. One was the Gorch Fock; another was the Horst Wessel. The latter, of course, was turned over to the U.S. after WWII and became the Eagle.
In the text of the book, Underhill meticulously gave the dimensions of all the ships in the class. All of them were different; they differed in length by more than twenty feet. The drawings were based on the plans of the Gorch Fock, which was, if I remember correctly, some twenty-four feet shorter than the Horst Wessel. Underhill was absolutely up front about this point in his text. Unfortunately, though, the drawings later got sold with the name Eagle attached to them. I'm pretty sure that almost all the wood and plastic Eagle kits have been based on those drawings - and therefore are too short. The one exception, as we established in one of those earlier threads, is the 1/200 plastic kit from Imai. That one appears to have been based on accurate Coast Guard plans.
As rcboater points out, the most accurate plans available are those offered by the Coast Guard - and the price charged by the CG Museum Northwest is extremely reasonable. Another source of information is the Coast Guard Historian's Office, in Washington. The head of that office, Dr. Bob Browning, is a first-rate gent and sympathetic to the needs of model builders. It's worth a look at the history section of the CG website: www.uscg.mil .
In about 1994 the CG Historian's Office commissioned me to do a drawing (outboard profile/sail plan) of her as part of a series of Coast Guard Cutter line drawings. I worked from the plans in Bob Browning's office - including the sail plan rcboater mentioned, as well as a few other sheets labeled in German that the Coast Guard had managed to get hold of after the war. (They were clearly labeled "Horst Wessel".) She's changed quite a bit in appearance since the fifties, but if my drawing will do you any good I think Dr. Browning will send you a copy at no charge.
The Eagle is an extremely well-photographed ship. Pinning down her precise appearance during the fifties will be a bit of a challenge, but it probably can be done. I seem to recall that the Mariners' Museum, where I used to work, had quite a few good b&w photos of her that dated from about that time. Unfortunately the MM charges outrageous prices for prints.
At any rate, my suggestion would be to start with the CG plans and see what the CG Historian's Office has to offer.