Welcome to HNet, joshkeith.
The ages of the characters are never revealed (except for Abraham Lincoln Hogg by his driver's licence, and therefore his twin brother, Boss), but the subject has been discussed a few times before. Here are three threads to get you started:
Ages of dukes
I have a question???
What were the real ages of cast? Anyone know?
Aside from the flashback episodes ('Go West, Young Dukes' and 'Happy Birthday, General Lee'), and the shown-out-of-order season 2 episodes, I think Dukes ran chronologically, although not many storylines crossed episodes or seasons. An example of this is T.C. Rogers becoming Supervisory Administrator of Hazzard County in 'People's Choice' (S2E11), but then she was never mentioned again. Of course, the 2005/2007 movies completely ignored the canon of the TV series, but that's another story!