secluff's post in name that piece? was marked as the answer
Those small plastic pieces at the upper rear of the fender are what Ford called a "Front Fender Filler." They were production installed until 6/1/71. After that date, the engineers decided they were no longer needed. The 71 Cougar also used the same piece, and they can be difficult to find since many of them have deteriorated over time and were not installed for the entire production year. Part number for the right side is D1ZZ-16570-A (ID# D1ZB-16570-AA,AB,AE) Left side D1ZZ-16571-A (ID# D1ZB-16571-AA,AB,AE). As you can see, there were three suffix number changes on the engineering number, but the part number never changed. For some reason, Ford continued to use a similar filler at the rear of the front fender for the 72-76 T-Birds.
As previously posted, there was a small run of these made and sold on E-Bay, but with an inflated price since the word "Boss" was used in the description. The used set for $60.00 + shipping is the cheapest I had seen any of these offered in quite some time. These rarely show up in any decent used condition.
As Don C posted, when you get a chance, please tell us some more about yourself and the plans you have for your '71.