Since I have owned and driven my '70 round-tail in the Chicagoland area
for 25 and restored it twice during that time I feel like I can comment
on this subject with some authority. I would be very suprised if your
car did not come equiped with the valence seam caps originally. I would
not be surprised by the fact that, after being driven in Chicago winters
for a couple of years, that they probably rusted to the point where the
PO pulled them off the car.
As pointed out, during my recent restoration I acquired the caps from
Spitbits. Get'em, they really will finish off your round-tail look,
you'll be glad you did.
On a side note, Chicago winters and salt were typically much harder on
the sills and passenger foot wells than on this rear valence area. As
pointed out by recent discussions on the list these portions of the car
are much more important structurally. If you haven't checked those
areas thoroughly, and I mean really thoroughly, I recommend you do so.
Ron St. John