Airconditioning=??

Any one know about adding airconditioning to the rear area of our gen1 & 2 vans ? I have an underdash unit from a 70 chev pickup that was given to me . It will fit under the dash perfectly. Im just curious as to adding a rear unit ? Maybe from a later model van -mostly a gm unit?? Whoose dun it ? I also will be adding a rear heat unit from my old gen 4-5?? 1986 van to it. Help & suggestions are apprecieated-Tahnx.