I'd probably remove the old dropouts, then see if I could bend the tubes (technically called cold setting if your not a gorilla :) )to allow the slots in the tubes to meet with the tang on the dropouts. I did this a little with the seat stays on my MTB, I brought the ends of the seatstays about 15mm further forward with no ill effects (actually the seatstay seat tube join broke on one side, but that looked like a crap braze from the factory anyway). You will need to bend both seat and chainstays together but I think it could be done ok :)
I'd probably remove the old dropouts, then see if I could bend the tubes (technically called cold setting if your not a gorilla :) )to allow the slots in the tubes to meet with the tang on the dropouts. I did this a little with the seat stays on my MTB, I brought the ends of the seatstays about 15mm further forward with no ill effects (actually the seatstay seat tube join broke on one side, but that looked like a crap braze from the factory anyway). You will need to bend both seat and chainstays together but I think it could be done ok :)
extending the tubes is not going to work.