Picked up this torsion bar during a farm clean up and wondering what it fit? TIA

According to Firmfeel, a 44 inch long Torsion Bar fits '65 -'73 Plymouth and '72-'73 Dodge C-Body cars (Fury, Polara, Monaco, Nwport, New Yorker).

A-Bodies used 35.8 inch bars, B and E -Body cars used 41-inch Torsion Bars whereas some C-Body's used 47-Inches, while those few years used 44" long bars.

http://www.firmfeel.com/c_body_mopar_torsion_bars.html

A 579 is:

Chart Number: 2269571
Side: Left
Color: Brown
Length: 44.0 In.
Diameter: 0.960 In.
Hex Across Flat: 1.41 In.
Preset Angle: 40 Degrees

Here are some online articles on torsion bars:

http://www.hotrod.com/how-to/chassis-suspension/mopp-9910-torsion-bar-restoration-and-detailing/

http://arengineering.com/tech/torsion-bar-tango/

Cool, thanks for the links.