I pulled an HVAC from an old Oldsmobile, and it's almost exactly the same as the thirdgen one, except for the vacuum lines. Does anybody have any idea which stock vacuum lines should go where in the Olds harness?

 

What model Olds, and what year?

This is the factory F-Body setup:

 

Oldsmobile Cutlass Ciera... I'm not sure what year, I found it in a junkyard and don't know too much about Oldsmobiles. Maybe somewhere from 86-90?

Thanks for that diagram! Does anyone have one from an Oldsmobile from that era? Hopefully the vacuum lines will be at least similar.

Also, the purple line splits with a Y connector and joins a grey line and both the other purple line and grey line connect to a different part of the stock HVAC. What do they do, and where would they hook up on the Olds one?

 

Grey is the heater control valve. It doesn't "split" off of the purple line; but the 2 do share a rubbery connector thing. The purple line is the vacuum "supply" from the accumulator. Looks like neither your Olds control head nor Vader's diagram shows that connection. There would need to be another little vacuum switch thing on the temp slider, to work that function. It's not impossible that your car's would attach to the Olds piece and work fine.

AFAIK all GM cars use the same color codes for those vacuum functions. You should be able to splice the lines together with some small tubing of some sort, and they'll work the same way with the Olds control head as they did with yours.

 

So, I could just let that extra rubber connection thing to just hang there, and everything would work fine? Would there be noise of a leak coming from those two lines that I should worry about?