Longshot, but here goes. Re-doing quarters after a body shop "installed" new quarters and this piece got mangled up pretty bad. It is spot welded between the drip rails and the rest of the inner structure behind the quarter glass. There is a piece that wraps into the quarter panel at the quarter glass window felt area. Piece needed: Where it goes:
Joe Vega (www.azchevs.com) should have what you need. Have not met anyone who cuts up cars to the degree he does.
Joe got back to me and said he should have the piece, but I'll let you know if things fall through. Thanks.