I've heard that the stock zetec 2.0l alternator puts out 18v if not connected the the ECU. is there any truth to this? I'd like to use it on my engine, since all the mounts are already there, but if it won't work what other options does everyone else out there run?

Not true. Zetec E alternators as in mondeos have a built in regulator.
ECU controls charge rate on Duratec alternators and probably Zetec S ones as well.

I run a standard one just fine, standard Bosch style one, nothing fancy. Plenty of output for jump starting BEC...