I have a 54cm 1986 Centurion Ironman, and a 1993 54cm Rossin bike. There is a 2 inch difference between the bikes from front fork end to rear drop out ends. What does that mean in handling difference if any?

Can't you tell the difference when you ride them?

BTW 2" is a lot of wheelbase difference for two, otherwise, bikes of the same general intended use. But wheelbase is what I call a resultant not an design input. Go and experiment with the free version of BikeCad and watch how the wheelbase shifts with tube angle changes and other design inputs. Note that the wheelbase isn't an input factor offered...

Some will claim that the shorter wheelbase bike will feel quicker in changing directions, others might say the same but instead claim a loss of stability. Hence the problem of using words to describe sensations. Andy.