The following information is based on the 1970 Mustang Shop Manuals, illustrations, and personal observations. Any inaccuracies are purely unintentional.
The colors used depicting the lines in these diagrams indicate the stripe color of the black vacuum lines.
Distributor Diaphragm and Vacuum Control Valve Operation
302 2V Imco Emissions with Air Conditioning Dual Diaphragm
302 2V Imco Emissions with Air Conditioning Single Diaphragm
302 2V Imco Emissions Non A/C Standard Trans Dual Diaphragm
Boss 302 Non Ram Air Dual Diaphragm
Boss 302 Ram Air Dual Diaphragm
351 2V or 4V Imco Emissions Non A/C Single Diaphragm
351 2V or 4V Imco Emissions with A/C Single Diaphragm
351 C Ram Air Dual Diaphragm
351 C Non Ram Air Dual Diaphragm
The Mustang 428 and Boss 429 engines use the Thermactor Emission Control system used with the Boss 302 engines. The Boss 302 schematics apply for these engine applications also.