I am not able to envision exactly what you have but you will, in all likelyhood, need the refrigerant hose from the 81 car. Is there any way you can compare the condenser connections between the two cars? This may be another issue. The exp valve should be located in the vicinity of the evaporator. You may be able to stick with the existing expansion valve. There should not be an issue with this arrangment as long as you stick with r12.

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Jim