The whole front frame assembly is known as a stub frame, and bolts to the body shell essentially under the front seat area.
I believe you can replace it with one from any 66 Plymouth Fury. Although they look nearly identical, Dodge and Chrysler stub frames are longer and won't fit.
Here is a picture of a 1966 stub frame. The area at the top is where the cross member goes.
hi ross...there isn't a lot of these cars around...not sure where to find a doner or one that's already out...could be u know where?...appreciate any help...thanx