Sounds like a job for Dr. Frankenstein
Wenches are hard to rebuild. Winches, on the other hand, are quite easy to deal with. If the winches on your 1978 boat are original, then chances are they are a model that is no longer in production. The best you can hope for is that the company is still in business. The winches on my 78 Oday 23 were made by Lewmar. Even though the models were out of production, Lewmar provided me with a free service manual. They were less able to find me a replacement part that I needed in order to avoid replacing the entire winch. If all your winches need is a little TLC, its actually easy to do. Check the archives of this site for lots of good advice. I did, and in combination with the service manual, I was able to make my winches click and clack like new. If you do need parts, I found this business "Yacht Service and Resources" in Newport RI (401-849-8470)that was unbelievably helpful in finding the replacement winch parts I needed. I can't say enough about the customer service I got with them; even though I only bought about $70 worth of parts, they did a world-wide search and found the discontinued items I needed somewhere in a warehouse in England.