I like the service manual for A/C info and vacuum lines. I have a paper copy and most years are available in PDF format.
http://67-72chevytrucks.com/vboard/s...d.php?t=558016
Vacuum is optional. Some people just have a manual valve they open in winter, and permanently fix the fresh air vent closed and the recirculate door open, and if you want fresh air open a window or vent a little bit. I like recirculate full time, no fresh air for me. My vacuum operated vent doors don't work quite right, I need to work on them. I'll probably just get them going and then hook them up to vacuum full time and bypass the vacuum switch.
The routing/hookup depends on whether your vacuum switch has 3 ports or 2 ports, and whether your heater water valve is open with vacuum applied or closed with vacuum applied. There are a couple different layouts.
Also the service manuals have the electric diagram. There are a couple different versions of those as well, the simpler one here from 1969 does not have an anti-dieseling relay, some years do. I doubt with modern gas anybody needs an anti-dieseling gizmo any more.
