I THINK I can answer this...
Are you familiar with idea of "VTEC" done by honda? (Called several other names by other companies with similar design) The idea is based on the principle that an engine can pull more power at higher RPM's by advancing the timing (I believe it's advancing at higher RPMs), but by doing so, you'll lose a little bit of your bottom end. The same goes for reversing the situation. So Mercedes originally designed "Timing Control" (not the proper name, I know) to where the engine would automatically advance/retard the timing as needed by the motor to pull the very most from the engine. They never perfected it, and scrapped the project. Honda adapted it and made it work. Over the years, several companies made their own design (Nissan, Subaru, Chrysler, Ferrari (and might I add that Ferrari's is the MOST complex EVER), and eventually Ford)
If I'm not mistaken, only recently (being like...2005, I wanna say) did ford start putting their idea into their market of cars. This also helped them to claim back a little bit of the fuel efficiency for V8 motors.
Thus...the new design is a "modular" design, hence the odd crank pulley and 3valve system.
There you have it. We drive a "Modular" engine.
Please, feel free to correct me if someone proves me wrong...
Through the years, many