4 door steering shaft same as 2 door?

Was the 4 door manual steering? My guess would be no.
In this case it doesn't matter, but there is a difference in the wheelbase between a Dart 4 door and a Demon.
Generally speaking, from the firewall forward, they are identical in dimensions. The only difference would be the options, such as power steering, disc brakes, engine, etc.
You are in a unbolt/bolt in situation when it comes to compatibility.
The steering shaft length is the only difference in the columns between power and manual steering.