You ask about is the "sync system worth it?" I will say defiantly " yes " and particularly for you because of the amount of time you are working in that rig,....give your self a little pleasure to make your day.
I would think that under the conditions that you outlined,...primarily a WORKING TRUCK, you should go with the 4.30 gear ratio and expect to loose 1 to 2 MPG at highway speeds over the 3.73 millage but you would probably break even if you are working the truck and using the 6 speed transmission in the lower gears if you had the 3.73 verses the higher transmission gears with the 4.30,....so your call but I would go with the 4,30 and you will probably still get better overall millage than your current V !0 and have more power.
Here's my 2 cents. I ordered the 4.30 gears for my F350 to maximize the power. It sounds like guys with the 3.73 gears are having to run in 5th gear at a higher rpm while towing. I thought with the lower gears it would be able to stay in 6th gears running at a lower rpm to increase fuel economy. I will soon find out, it sounds like I should get it in 3 weeks.