Heater and ductwork difference?

[wilkin250r]

Is there any major difference in the heater and A/C ductwork between the years?

I've got a 79 in poor shape, and it came with a 81-87 style dashboard (also in poor shape). As far as I can see, the 81-87 style dashboard fits just fine with what little ductwork I do have under the dash, I just also have to match it with the proper bezel.

What about the rest of the ductwork? I found an 84 (or maybe it was 81) at the junkyard in decent shape, and I was thinking about pulling every piece from under the dash, complete with vacuum hoses and possibly even some of the wiring.

I know there are a few differences in the AC selector switch itself, but are they basically the same beyond that? Will I be able to route the proper vacuum lines and control cables for the blend doors?

What about the other half under the hood? A/C lines, compressor brackets, and everything else the same? I've already got an 84-style front clip on my 79, so mounting for the air conditioning condenser is no problem.

Basically, if I want to pull all the heater and A/C pieces from this 84 to put in my 79, what will fit and what won't?