Thanks for your question and post about 1975 Bordeaux.
The biggest issue you have with 40 year old wines is their provenance. On the bright side, there are fine 1975 Bordeaux wines, that are easily in your price range. Do you like 40 year old Champagne? I have friends that love old Champage, but it's quite different in character than young wines, in case you are not familiar with older Champagne.
I've never had 1975 Gazin, but it could be good. It's made to age and 1975 is fine for Pomerol.
You should use the search function for tasting notes and type in 1975 Bordeaux.
A few wines I've had I recall tasting and liking are 1975 Pichon Lalande, 1975 Montrose and 1975 Le Gay. Sauternes made very nice words, but that for dessert, not the center of your dinner.
To read details the 1975 Bordeaux vintage, please see http://www.thewinecellarinsider.com/win ... ying-tips/