1999 Ford Mustang V6 Starting Problem

If you have a pepboys or napa nearby, they sell this cheap widget that a spark plug cable plugs into and you clip onto the engine or ground. Once you start, it will throw a spark across a gap.
Since you replaced the coil pack, it could be that the old pack did damage or maybe the new coil pack is damaged. In other words, the bad coil pack may be a symptom - not a cause.
That’s why it is important to make sure you have spark.

Edit: here’s the one sold by autozone


This one seems to plug in series with a spark plug.

Here’s the one sold by NAPA.
http://www.napaonline.com/Catalog/CatalogItemDetail.aspx?R=SME705931_0215388768
This is the one you plug the wire into and clip onto ground.