I'm no expert on the topic, but I think I can safely say that this is not a Mustang air cleaner...
With those wide looking air ducts (with no valves), I don't know what it IS from.
Hopefully somebody in-the-know will chime in;).
1994 F150 4x2 Flareside. 5.0 w/MAF, 4R70W, stock.
1984 F150 4X2 Flareside. Mild 302 w/ 5spd. Sold.
1980 F150 4X4 Flareside. 300i6 w/ 5spd. Sold in 2021.
1980 F100 4X2 Flareside. 351w/2bbl w/NP435. Sold in 1995