Would it be worth it?
 

Doing some research today I found some specs on the read end in my truck, it weighs in at over 550lbs!!!! It is a 3/4 ton, but that still seems excessive to me. There are two lighter duty options that would bolt right in (only changing the u joint) that are considerably less weighty, 200lbs and 230lbs. I have worked really hard with mods and driving habits to get from 15 hwy stock to 21-22 combined. If I decide to do the swap I could try and find one with more hwy friendly gears, I have 3.73 now, maybe a 3.08 or 2.something. Worth the trouble and expense?

I imagine the gear ratios would help more. Weight reduction has its place when accelerating but probably won't do much at all for cruising. A higher top gear will help you whenever you're using it- that is, whenever you're driving on a highway! :thumbup:

You have a "warm air intake" and no gas logs. Not much to go on. :/

...the EPA claims 1-2% improvement in MPG for every 100 lbs reduction in 3,000 lb range vehicles, so a 300 lb reduction (550-250) should be worth about 3-6% improvement.

...however, the 3.08:1 axle ratio will net a BIGGER improvement, for sure, although your "load-hauling" capabilities will go down.

Yeah, I haven't gotten around to updating my stats on here as of yet. A quick rundown on my truck would be......93 Chevy C2500, TBI 350, 4l80e, and 14 bolt semi-floating rear with 3.73 gears.
Mods are warm air intake, full tune up with plugs gapped to 52 and timing advanced 4* btdc, new 4.3 injectors ( smaller with less flow at stock fuel pressure), adjustable fuel pressure regulator running 5psi over stock pressure (with the smaller injectors I get almost the same flow as stock but it is a much finer spray that atomizes much better), K&N 3x14 element, stock y pipe with 3" pipe and high flow cat with turbo muffler ran to just before the rear axle, underdrive pulleys and twin electric fans wired to two toggle switches so I can engage them one or both at a time when needed. Also I found a set of 15 inch alloy wheels to replace the stock 16's, with 245/75/16's they weighed around 90lbs ( will get more accurate measurements). Now I'm running 235/75/15 because they are a third the price, narrower, don't look tiny, and tires and wheels weigh right at 50lbs each. They also lower the vehicle about an inch.

Also I moved my road box to the back of the bed butted up against the tailgate, and slip my tool box right up behind that to try and simulate a partial bed cover, I don't think it helped with economy but it makes a nice work area when the tailgate is down.

Have you corrected your speedometer / odometer for the smaller tires? That will affect your actual vs. indicated miles per gallon.

Yeah, measured the circumference of new and old tires to get an accurate measurement of the difference, then figure that in to the mileage listed on my "gas notebook"