Lifted from another member:
"M88 on an E-body is rear deck lid (chrome) moulding, M88 on a B-body is the quarter panel tape treatment, this common code for two different trim options on two different body lines IS confusing leading many to assume that M88 on an E-body is the Billboard or Hockey-stick stripe (which of course is V6*), the * denoting the color of stripe."
Its the (chrome looking) stainless steel molding around the rear of the tail panel.
I also forgot to ask, are you going to repaint the interior as well?
B