They have a universal short antenna at Walmart for less than $8.00. It has several threaded options...just insert the Ford threads and install in a minute. No difference in reception vs. stock. It's black and looks relatively very cool for coming from "Wallyworld"...did I mention it cost like $8.00 inlcuding tax!
In the end, the only thing that is important is how well you can hear the radio stations that you want.
The following has been posted previously, but I thought that it might be useful to post again. It gives you a relative reading on the strength of your AM or FM radio signal.
Have the audio system set for either AM or FM, and tuned to the station whose signal strength you want to measure.
Simultaneously press and hold preset buttons 3 and 6.
This puts the audio system in walk-around mode to test the speakers.
While in the walk-around mode, press preset button 3.
The signal strength is displayed on the radio.
I had a 14" shorty on my car and it was easily as good as the stock unit. Zero loss in quality/range.
Then when the 88 year old ****er hit my car, the body shop was careless and stuck a 4" dealy (looks like something off an audi, VERY nice looking...) not so hot on the reception though. It's not terrible, but it doesn't match the 14" and stock performance.