Can be 4.6 ally, 4.6 iron, or 5.4L iron; 2,3 or 4 valves per cylinder; different main cap designs 2 or 4 bolt; girdled or not; various sumps.

The basic idea is that it's a common platform sharing ancillaries and potentially able to share things like headers/inlets.

N.B. have just typed this without any googling so may be off on / missing some of the details!

Chris