You can get the keys on ebay a lot cheaper with instructions on how to program it. There is a set of two for 16.99. Just type this in "1997 ford mustang transponder"
-Mac CAI, 73mm Mass Air
-Dual Flowmaster 40s, H pipe, 2.25 in pipe
-42% Underdrive Pulleys
-4.10 Gears & Trac-lok