I have a friend in my local Firebird club here in WA with a 69 Sprint convertible (I'm sure you know him from your OHC group? Brad) Anyway, he's building his extra 68 Sprint motor into a monster 6! Completely built, cliford intake and headers, AND a supercharger! Now some might consider that getting carried away, But I think it's great!
68OHC is right... you can easily get close to 300 HP with out going overboard! And there are a lot more options out there now for the OHC then there was when I had mine in 83'... wish I still had it!
I say go for it and enjoy it! It's well worth the effort!