Vacuum diagram for 1988 Volvo 740 gle can be found online in the images section of google search. The search should be done with the keywords 'vacuum diagram 1988 Volvo 740'.
you can find it in a workshop manual
You can find a 1986 Winnebago, with the Chevrolet 454 cubic engine, vacuum routing diagram at most Chevrolet dealerships. The vacuum routing diagram can also be found in most Chevrolet engine service manuals.
You can find the 1986 Chevrolet vacuum line diagram at most Chevrolet dealerships. The vacuum line diagram can also be found at most auto-parts stores.
There should be a diagram of the vacuum lines on the passenger side shock tower.
Chiltons service manual
Haynes Repair Manual for Volvo 760/740 has diagrams of the vacuum sub-systems.e,g. the EGR, the ignition etc
the diagram you are looking for is on the fan guard connected to your radiator
usually there is i sticker on the core support showing the vacuum diagram. If its not there then i would spend 20 bucks on a chiltons manual.
One can find a wiring diagram for a Volvo 245 at Turbo Bricks. These can also be found at Volvo Club and at Volvo Tips.
A local Ford dealer should be able to supply the needed diagrams for the vacuum system of 1986 Ford 351. They keep these items on hand or know where to find them.
Which vacuum diagram The Underhood for the engine or the vacuum for the interior /AC system?