The module is a common failure. However, take a look at the basics first.
Is the distributor spinning when the engine is cranked? Does the engine turn over very easy or sound pretty normal when cranking?
If these are both good, then the module is where I would go next as well.
As mentioned, there are two style. The smaller normally Grey style is mounted directly onto the distributor.
The other style is Grey or silver (normally) and mounted on a fender well. A VERY IMPORTANT thing to keep in mind. If it is the fender mounted type there will be either 2 or 3 plugs coming out of it. Right where these plugs (the wires themselves) go into the module the wires are bound by a colored chunk of rubber. There are several colors (Black, red, orange, yellow, blue and some purples). You will need to know this color in most cases when getting a new one as Ford uses many Federal emission differences in the era of the vehicle you are working on.
Good luck...