Intermittent no start, 89 GMC 5.7 TBI

[superdave]

My dad's 89 has an intermittent no start issue. Most of the time it does fine. Occasionally, it will crank but not start. I borrowed the truck a couple of times recently when my family was down a car. On 2 different mornings, I was leaving for work and it wouldn't start. Later in the day (both times) it started fine. Since it is now running fine (and I can't troubleshoot what is running fine at the moment), any ideas? When it wouldn't start, I didn't have time to troubleshoot at the time since I had to get to work. I did shoot a little starter fluid in it the first time with no results, so I'm certainly leaning towards spark.

First thoughts are coil and module

 

[89RCLB]

Ignition module would be at the top of my list...