If you are talking about the large silver/black lettering decal on the left shock tower, I wouldn't worry about exact placement.
I've seen originals placed in all kinds of locations, including rotated 90 degrees. Ford took no particular care in placing them, so anywhere below the wiring harness would be correct as far as I can tell.
I'm pretty certain I am right about this, but someone like Charles T, or Jeff S's opinions would be the really valuable feedback on your question.
I also share with Mustang_GT dilemma. Searched this forum and the internet last night for hours and found no answers for decal placement. I have this kit that includes something like 15 decals/no directions for general location.
I am sure many of us have bought this kit. Most have people in their area that they can "copy" from. But if you live in a rural area and have no one to copy from then you have problems. Seems as if this should be simple challenge. Not on where you have to spend $15.00 for a book, or have to be just wait and hope you find somebody that can help. Some in the past have given a phone number of a guy that can help. Can you imagine everybody calling him?
Sooo the bottom line here is that I can use this assistance just like many other people.