Sound familiar (coming from me), like most things Cobra chassis manuals are not that simple.
We have accounted for three different versions (so far) from the production period. The content in the books changed as the specifications of the cars changed. Original owner car manuals have had brass screws or aluminum screws.
Then owners could and did get copies of what was on hand from either a Shelby company or AC Cars into the late 1970s. Based on what people have displayed it must have been an accident to get any particular version. If it matched their chassis range okay if not too bad.
So many originals seemed to have been distributed with the cars or through the parts departments that originals in good to horrible condition are not all that rare. The rare book is the one taken out of its Cobra near day one and kept in mint condition well away from roadside, shade tree, or shop use.
'Reproductions'. Some time before 1983 when I bought a reproduction to use as a shop copy a photo copy an original became readily available. The holotype book they used to photograph had a hand written cross reference in it. Somebody had noted that the AC Cars 187-337
oil seal was the Ford/Shelby part number S1CS-1180-A. That note was not removed before production of the new replacement books. Missing from the photo reproductions were some information regarding the original publisher and price for the book. Since that time several companies and at least one club have had their own replacements created and distributed. I talked with a rare literature dealer at a big event once and he told me he could order all the copies of "originals" that I wanted.
Details, details. The common reproductions have something dimensionally different from any original that I have measured: the over-all length and width, the weight of the page stock, the weight of the cover stock, length of the screws, total thickness of the entire book, texture of page or cover stock, color of the cover stock, etcetera. The photo copy that I bought in 1983 has slips of paper stock inserted in the binding as shims to help fill out the space for the long fasteners the producer used. I have not examined the expensive reproductions but I am told that at least one is very convincing especially if aged a little. A clue to origin that some people use is the clarity of factory pictures. Pictures in original manuals are of decent quality and many fine details can be seen in assemblies. The common reproductions lost finer details in their picture illustrations, the copy or copy of a copy not being as clear as an original.