I'm not getting heated air through any of the vents. I'm thinking busted vacuum line somewhere causing the heater door not to open or close from the controls on dashboard temperature controls. Any other thoughts of what it could be? I've changed water pump recently, antifreeze is good, thermostat is good. Never checked heater core if clogged or not but I don't think that's it.

 

Welcome to the site. It could also be your heater water control valve.

 

As Eric (oldcutlass) mentioned check your heater control valve, are you heater hoses hot to the touch? Report back when you get a chance
Eric H

 

Unlike the earlier cars, the 1973 Cutlass used the normally open heater control valve (1972 was the last year for the normally closed valve in the A-body cars). It is very rare (but not impossible) for these valves to stick in the closed position. They only close when the A/C is in the MAX COOL position. Far more likely is a problem with the temp flapper door under the dash, or a clogged heater core.

 

Didn't think of that change...

 

I didn't check to see if heater hoses are hot to the touch yet, but when I put the control on the cold side I get cool air. When I put it on the hot side it very slightly warms up a little but still cool air. Which leads me to believe flapper door barely moving.

 

Under the drivers side up behind the radio wiring you will see the vacuum lines going to a round type of module. listen for vacuum when pulling the line off one at a time when moving from defrost to heat. You should hear the door open and close.
If the flapper door is stuck you will only be getting air coming down by the floor it won't blow up top when moving the select to defrost.
You could have a clogged heater core as Joe indicated.
When you changed out your water pump how did the antifreeze look when draining? Did it have a rusty or orange tinge to it? A little thicker when draining from the petcock? This would give you more indication as to your heater core being clogged.
Also if you used stop leak of any kind in the past, chances are the excess tried to go thru the small heater core tubes and clogged them.
Hope this helps
Eric