Heater and A/C vacume lines

[Motor City GMC]

Can anyone tell me where these originate from and enters the cab and then how they run after that?
I have heat and the cold to hot control works but i cannot switch between floor defrost vents etc... I know i have a couple that are broken so im looking to just replace them all with new lines and want/need to know there routes and also where they come from in the engine compartment because i want to replace that lines as well and because im about to eliminate as many vacume lines in the engine as possible but dont want to lose this one.