Maybe I wasn't clear. I have a Ford OEM alarm in my Merc. Villager (Even has a Ford Oval on the Alarm Siren). It was dealer Installed. It is actually a Clifford (owned by DEI) system.
If it is a dealer installed OEM option, it is actually often made by someone other than Ford. Clifford is a large supplier of OEM equipment. So when you say you only want a "Ford" system, you would still get the Clifford or other sytem anyway. It is cheaper to get an alarm/remote start in the real mfg's name then to get the "Ford" label on it. The Mercury Alarm was $900. The Viper was $299. The Merc. alarm was an add-on to the remote keyed entry module so didn't need a key fob . The Viper was a much better deal with longer range and more options.
I originally wanted the original system (on my Contour), but was taken aback at the complexity and cost. Save your $ and get an aftermarket system. The local alarm guy will treat you better than any Ford dealer. As far as Astrostarts, if that floats your boat, fine. Why they are better than any other in particular I wouldn't know.
Just my opinion anyway.
