It's a upper control arm from a 1955 S series Rolls Royce.
While on tour at AME Craig showed this project to me. I guess it was to be used as a limmo with a big block chevy back east somewhere. The frame rails are rotted through in several places and even beginning to buckle over the rear end. AME was contacted to make a new "bolt on" chassis.
The crew at AME can build pretty much anything you need. This and a few other projects we talked about proves it.