New reproduction left front seat mount bracket for 240Z, 1970-73.  These are modeled after the originals and made out of stainless steel.  The metal is a little thicker than the original sheetmetal for better strength.   These have only been tested on 70-73 240Z, may fit later years or may require alterations. 

Left front bracket.  See other listings for right front and rears.

*Stainless steel can be welded to mild steel without any special welding materials or techniques