To be honest with you I wouldn't use any of those lenses. There are a lot of things you can cut corners on but the lens on your camera and the lens or your enlarger are not one of them. You've got a few issues. First of all updated lenses are available. I purchased a mint El Nikkor 2.8 (latest model) for about $40 shipped. I paid about twice that for a Schieder 80mm f/4 Componon-S. Again it was a mint copy. If you are patient these things pop up at similar prices often enough.

What I find with older lenses besides outdated lens design is they either have fungus from humidity or haze from long term exposure to dark room chemicals. The person who sold me one of my enlargers told me what a great deal he was giving me and how I could sell each of the lenses on ebay for $50 a pop. Total nonsense. Often buying an enlarge is the inexpensive first step. Getting all the lenses, carriers, filters, easels, etc quickly runs up the cost. It is still relatively cheap but that free enlarger you got and the $8 lens will not produce the sharpest prints. It's better to invest a little more money and have something you don't have to wonder about. $40 for a 50mm 2.8 El Nikkor is very reasonable.