If I'm not mistaken you are talking about lenses that are good 30+ year old. If I remember correctly, back then, Nikon did not make consumer grade lenses and professional grade lenses. They made LENSES - just one grade, pretty much. So everything else being equal, f/2.8 would be a better lens.

But.... are they really in equally good condition? What are the price differences? Being a wide lens, focusing isn't all that critical. Plus, you are going to use this lens on a film camera, so you won't be doing crazy things like viewing the image at a ridiculous magnification and stress over sharpness....

If I were in your place, I'd get the f/2.8 if the price premium is small and it is in good shape. Otherwise, I'd get f/3.5 and be happy.