Yes its possible you have to decide which set up you want. They make an after market unit that hangs under the dash that’s pretty big and gaudy. then you can order after market parts and pieces from LMC truck parts which are omc replicas.or you can go to a junk yard and get all necessary pieces . Good Luck
PS aint none of these options gonna be cheap.
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Yes. Some places sell the conversion kits to add A/C but they can be expensive. You could find a similar truck that had A/C and move it over to yours. It will be a lot of work, make sure you have a free day or two to do it.
Best advice, make due with rolling the windows down.
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How old is the truck? GM may have a complete kit, but it’ll be costly.