if you are positive they were not expensed then try just inputting the asset using the "original" date of purchased or placed in service with the amount and the correct asset type. It should calculate the depreciation report and there is a line on the input worksheet where you can manually input prior depreciation. See what that does. But. . . . 

I would lean to they were expensed somewhere in the last 35 years and not try to do this now.