If you search the site you will see they make a model with a smaller cap (small block size) and external coil. This is the version they recommend for A Bodies. The control module is mounted on the side.
Here's a link to the DUI "Dodge Tri-Power Ignition" distributor with the smaller cap, externally mounted module, and separate coil. They specifically say "This system is ideal for small blocks in Darts, Demons, Dusters and pre-1970 Barracudas that also cannot use the DUI."
