If it can be aligned within spec, I would think that the tie rod is the correct length.
Also, the alignment can be within spec and the steering wheel not be centered.That can be fixed by adjusting the tie rod ends on both sides by an equal amount in the same direction. Mine is off a little bit, but not enough to encourage me to fix it.
Also, make sure you are checking your driveability on a flat, level surface. Many roads are "crowned" to make them shed water during a storm. This means that you are usually driving on the side of a tiny hill, making you hold the steering wheel slightly in one direction.
Are you sure it's an alignment problem and not a brake caliper dragging on one side?
There are several excellent write-ups in the "How To Tech" section of this site that will lead you through doing your own alignment and teach you about the steering geometry of these trucks. It's worth reading and getting under the truck to examine things yourself. I used these articles to align my truck when doing my lift kit and steering modifications. I actually had the alignment within spec when I took it for a professional alignment. It's not rocket science. You just need a good mental picture of how things need to be and what can or can not be adjusted to attain that goal. Bad ball joints will affect steering. But your alignment guy should have checked them before starting the alignment.
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