How to tell the difference

Hi everyone
How do I know if I have a 727 or 904. I have a 440 engine
Just started getting my Dart back together, and I noticed my first to second shift works (hits very hard) but no second to third.
Is there an external adjustment that can be made, or will I need a overhaul?
If I do need a overhaul any suggestions as to where I can send it

many thanks
George