Like HemiKiller said, you have the advantage of having the Internet, whereas most of us began our Mustang journey back in the dark ages when a dealership with a microfiche machine was high tech as compared to the folks who still used huge racks of paper catalogs to look up parts. And at our dealership the way information was disseminated through factory training, "kind of" with shop manuals (often containing incomplete information), or through monthly Technical Service Bulletins we would receive that would include some fairly useful information at times. But, nothing like what the Internet has made available to us.
Another advantage you have is a camera you can use without running out of file, or having to take film to a developer who would process the film for you - and you would get the pictures back within a week or so. So, I agree with the earlier comments. Take lots of photos BEFORE you begin to tear things apart. If it ain't broke, don't fix it - it is valid in general, but enhancing a component is fair game. Don;t go tearing off emission control equipment until you first understand what the system at hand is designed to do, and how it gets done. Some emission control systems aare benign, and others are actually helpful (PCV Valve, Fuel Vapor Recovery Systems, Thermal Vacuum Switches).
And you really need to start building a library of documentation. Most of my core manuals are from Forel Publishing. Here is a link to their site, where you can pick a model year, then purchase and download your manuals in PDF file format The pricing is quite reasonable.
https://www.forelpublishing.com/clickbank/index.html.
Prior to 1973 Ford did not provide amy really useful emission control or engine vacuum line routing information, and before 1972 their electrical schematics were lavking the kind of detail that 72 & 73 electical schematics have. I would begin with a 1972 color electical schematic manual, a 1972 shop manual, and a 1973 Parts and Accessory catalog (this particular manuals covers from 1964 - 1973, so 1972 parts are in it). and a 1973 shap manual. The reason for the 1973 shop manual is because the 1972 manual has no useful information on emission control systems (nor do the prior year manuals). But the 1973 shop manual has a lot of very useful information that is largely the same as you have with your 1972 Mustang.
The Mustang Barn put together a collection of engine vacuum line schematics, and made them available for no fee. I, with their permission, assembled their files into a master file grouped by year, then sorted by engine. They did a nice job. You can download the file from my Google Drive at:
https://drive.google.com/file/d/1YZJwYFyd7aIx8xM_hjOaowbVCi4yqgnP/view?usp=drive_link
Please take progress photos, and post your journey once in a while. If you have any questions or concerns, you have come to the right place. We have lots of really qualified and highly experienced Mustang folks in his forum.
