Vacuum supply 4WD

1996 Chevy Blazer LT. In the process of installing new engine and rebuilding the transmission. Its been awhile since I removed the engine, transfer case (http://www.blazerforum.com/m_50784/tm.htm#) etc. so I dont clearly remember where the transfer case gets its vacuum from. I am talking about the series of hoses that go back to the transfer case. I can see where they hook to the transfer case but where does it get hooked to up in the engine compartment as the vacuum supply? This is a push button 4wd system.

Thanks.

PVC supply off intake also has the vac over to the drivers side reservior where it Ts off to plastic heater control line and the transfer case supply.