Regarding plans of the Victory - I'm pretty sure the ones by George Campbell (referred to in Michel's recent post) are the ones I bought, via Model Shipways, about thirty years ago. They're blueprint versions of the plans Mr. Campbell drew for Longridge's Anatomy of Nelson's Ships. The foldout prints in the book are, if I remember correctly, 50% reductions from the blueprint versions. If you've got the Longridge book you don't need the Campbell/Percival Marshall plans - unless you just want bigger versions of what you already have. And the book contains those marvelous perspective drawings (the one showing the maintop is downright awe-inspiring) and detail views.
Lots of good plans for this ship have been published over the years. Ironically the primary source drawings, in the form of the "Admiralty Drafts" in the National Maritime Museum, aren't of great use to modelers; they don't have the sort of detail that's so often found in plans from that source. But the subject has attracted several extremely competent 20th-century draftsmen.
The first may have been Basil Lavis, whose set of Victory drawings was published, I think, sometime in the 1920s, when the ship was being restored for public exhibition. They're entirely competent drawings, though they don't contain the sort of detail the later ones do. (I suspect the Lavis drawings are the ones Longridge used to build his model. I think his publisher commissioned the Campbell plans after the model was finished.)
The restoration of the ship was supervised by the Society for Nautical Research, which commissioned a fine historian named R.W. Bugler to do research in the primary source documents. In 1966 (at least that's the date on the copy I've seen; the first edition may be older) Bugler himself published a book called H.M.S. Victory: Building, Restoration, and Repair. It's a big, bulky tome with a set of drawings folded into a pocket inside the back cover. I haven't seen a copy of it in years, but my recollection is that the drawings were excellent - though not as detailed as the ones by Campbell and McKay.
I like the Campbell drawings; they're fine examples of the drafting art, and I've never encountered any major criticism of them in terms of accuracy. (Here we should make the usual caveats: those drawings show the entry ports, knee-high forecastle bulwarks, and various other features that may or may not be correct for the ship's 1805 configuration. But I'm unaware of any set of plans that doesn't have that problem.) They're particularly useful to modelers when used in conjunction with the text in the Longridge book. The combination of those drawings with Longridges' verbal descriptions should, for example, provide the modeler with everything he or she needs to know in order to rig a model of the Victory.
The drawings in the Conway/Naval Institute Press Anatomy of the Ship volume, by John McKay, are superb. (I've done enough ship drawings myself to know that this man is an absolute master of the form. I'm not worthy to sharpen his pencils.) Here, though, the modeler needs to be careful. The first edition of that book drew some heat from reviewers because Mr. McKay included some decidedly non-original details, based on the ship's current state. (For example, he showed the wales as layers of thin planking fastened to the exterior of the hull planking. That arrangement is an example of modern economizing. The original wales were huge timbers fastened directly to the ship's frames.) Mr. McKay (all credit to him - and Conway - for their integrity) later published a revised edition of the book in which those errors were corrected. The modeler would be well advised to seek out the revised edition.
I read one criticism of the Anatomy volume to the effect that it was deficient in lacking a body plan. The critic should have looked closer and thought a little before he made that comment. True, there's no single drawing in the book labeled "body plan," but it does contain a series of remarkably detailed cross-sections that convey the same information - and much more besides.
Then there's H.M.S. Victory: Her Construction, Career, and Restoration, by Alan McGowan and John McKay. This is a terrific book, combining attractive, "coffee-table" appearance with a great deal of fine scholarship. The last section of it contains over a hundred drawings by Mr. McKay. At first glance they look like the same ones that appear in the Anatomy of the Ship volume, and some of them are. But for this book Mr. McKay prepared quite a few additional drawings, most of them dealing with the rigging. Both books are worth acquiring. For the modeler starting with a kit who can only afford one of them, though, I think I'd recommend the later, McGowan/McKay volume. It contains more information about the rigging, which is the area where the modeler working from a kit is likely to need the most help.