I have a 99 doing close to the same thing, I was told the ignition switch was bad about going out on them and to try that. Not high on my priorities so I haven't done it yet. I swap the PCM between it and my 97 for a cruise issue and the 97 has run fine since probably 2 years ago, it is driven most days. The 99 also ran fine for a time after the swap but I went ot move it one day and this, it has a bad trans so it is only driven as a yard truck, so I would be interested in what swapping the PCM can do.

Both of mine are 4WD/318/3.91s, virtually identical except for the color.