Can a 1996 Ford Taurus replacement ignition lock cylinder be fitted to the original key?

No, a replacement ignition lock cylinder for a 1996 Ford Taurus will not automatically work with your original key. The replacement cylinder will come with its own unique key or key code. You'll need to either get the cylinder keyed to match your existing key (if that's possible, depending on the supplier and cylinder type) or get a new key cut to match the new cylinder.