You didn't put what country you're in, so I'll work off the basis you're in the United States.
I think you're going to have a very hard time accomplishing what you're talking about after such an extraordinary amount of time. One has to assume that there would still be records that could be retrieved in order for anyone to determine the amount you'd have to pay, and after 40 years, the paper records would be long gone.
It's possible there might be microfiche somewhere, but I wouldn't have a clue how easy or possible it would be for it to be retrieved.
I assume you're wanting to repay this as a way to boost Social Security or other government benefits in your retirement, but it's really hard to say whether repaying the rebated money would make much, if any, difference.
This is really something you'll have to contact the IRS about, but unless they are trying to collect funds from you that they say you owe then it's highly unlikely they have any record of what you're asking about, and they probably don't even have a mechanism for accepting and crediting such monies. The real issue here is the amount of time that has passed, because there would be little compelling reason for the government to keep detailed records (they perhaps maintain summaries, but little else) for extended periods. We all have the impression the government knows all and never forgets, but that simply isn't the case.