I have a 1975 115 300d and it is the nicest car I have ever driven. Well, next to my 1967 Chevy El Camino 4spd. 327 it is. Don't worry about speed. You can go from zero to speeding ticket as fast as the next guy. You can also go from here to eternity at 75 mph and 20+ mpg. The car is big, comfortable, pretty easy to work on, and most systems ae fairly simple.

Check out www.collectorcartraderonline.com. They usually have a few 115's listed.