Incorrect. The distributor does move on your truck. The base timing is set by removing the SPOUT connector, then moving the distributor. You use a timing light to verify the distributor is properly set. Once you do that, put the SPOUT back in. The computer does control the timing with that SPOUT plugged in.

Your mechanic is not helping you any by making misstatements like they have. Find another mechanic who knows something and/or buy a repair manual to help you understand what needs to be done.

Here is another link to a technical writeup for upgrading the ignition components and bumping the timing up from factory specifications. There are some more photos and captions to help you out: ignition upgrade and timing bump