Sounds like the connector he's talking about is the cam position sensor (CMP) - I do believe the PCM will compensate if there's no signal from this, allowing the engine to run. Been too long for me to say with any degree of certainty, so others will have to chime in. Clearly it did run as OP has been driving the truck with it disconnected. Most likely, they simply forgot to plug it in after they installed the new distributor. Out of sight, out of mind. The distributor on a Vortec 454 is very much out of sight behind that big intake..
Richard