1973 Dart swinger- manual steering box

I'm looking for a manual steering box for a 1973 dart swinger. I'm not sure what the interchangeability is on these units between the years. I'm putting a 340 in and I want the room for headers.

I live in Rhode Island and a local parts yard said I could have one for $50. I'm not sure if this is a good deal or not, since I don't know the history on it.

Suggestions? Ideas? Have the part?

Thanks all.

-Mike