Replaced just about everything Ac won't work

This would be typical of a bad expansion valve except the low side should go low

You have enough R-12? The shop manual shows 2 lbs 14 oz "with a 2 row condenser"

Oh and.........do you have a shop manual?

Free download:

(Thanks to AbodyJoe)

[ame]http://www.abodyjoe.com/pictures/Misc.%20car%20info/1972%20Plymouth%20Chassis%20Serv%20Man.pdf[/ame]

Does your compressor have service valves, and could one of 'em be shut?

Are you absolutely sure that both service valves are getting depressed, or otherwise not plugged to the gauge manifold?

Is this the factory compressor? Maybe the EPR in the compressor is stuck?