rvrtrash, the heat shield in your illustration is the correct one for your 71 Boss. The longer heat shields in the E-Bay listing are for 72-73 applications. Your problem finding one is complicated by the one year only use of that part and when people hear the word "Boss". That shield was also used on the 71 LTD with 400 engine (LTD with 351C was different!?) 71 Torino 351C, 71 351C Stang, and sister Mercury vehicles. Ford number is D1AZ-9A603-A if you want to search by part number. The ones I've seen for sell must be made from some sort of precious metal! $$$
Agree with bkdunha on the E-Bay auction for the 72 air cleaner. Lot of nice item's there, just a little heavy on the freight charges.
Good luck on your search.