Took me a bit, but I found 'em
here.
The page has 1968 - 1973 Mustang vacuum diagrams. Scroll down to the bottom, Figures 120 through 125. Evidently there were several different setups for the vacuum system that year. It's up to you to figure it out from there.
Hope this helps!
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Ninjamobile
AKA The Mad Chauffeur
1966 Mustang Deluxe Coupe (302 V8, 4bbl Holley Carb, Edelbrock intake, custom headers, dual exhaust with Flowmasters and GT valance)
1981 Mercury Grand Marquis - AKA War, Big Red, Bessie the War Cow
2003 Dodge Stratus R/T Sedan - AKA The Ninjamobile.
73 mustang 302 vacuum routing needed 
