Looks like the distributor with vacuum and mechanical advance, which is what you need.
The next quest is more difficult. From the factory, all 5,0 Mustangs made from 1986 and later have an engine with a steel roller camshaft. That means you need a distributor with a steel gear to match the camshaft. If it is an iron gear, it will wear out very quickly and put iron shavings in the engine oil. Not a good thing.
If you have steel gear, then you probably have s distributor compatible with the DuraSpark ignition system used on Mustangs built before 1986.
LOOK and see if there is a part number or manufacturer's name on the distributor. That will help provide answers to the wiring and if the gear is steel or iron.
Use Google to look up the part number or manufacturer. Google is your best friend to find answers to things you don't know.
Here's the link to DuraSpark wiring :
Duraspark II ignition diagram:
Diagram courtesy of /www.billwrigley.com
See
http://webpages.charter.net/1bad6t/duraspark.html for more help.
Note the ballast resistor shown in the diagram: you’ll need that too.
If you use a coil from a 78 or later Mustang, you don't need the ballast resistor. The stock 89 Ford/Mustang ignition coil does not need a ballast resistor
A simpler HEI ignition that uses the same distributor and fewer parts can be found here. This is an excellent resource, and I suggest that you add it to your Internet Favorites
http://www.binderplanet.com/forums/showthread.php?t=48435