Distributor? Electrical Advance or Mechanical

It's intriguing that it would list both for an EFI application, unless it has them for those who have performed carb swaps. EFI Mustangs use electrical advance, and it's far beneficial to do so over both vacuum and mechanical advance distributors because you can control your spark advance much more precisely and under a wide range of conditions. IAT reading high temps = EEC pulling spark. IAT reading a nice cool charge = EEC advancing spark. Can't do that with a mechanical or vacuum advance distributor.

As previously stated I would bet that they are listing the mechanical for carb swaps. I got a carb swapped 92 with a mechanical distributor locked out with a MSD 6AL programmable where it has timing curved based on RPM that is programmed with a laptop.
If you have functional computer it is much better as it is using many outputs to decide the best timing at that moment.

Scott