Hey Fellas,
I am new to the site and chevy diesels.I don't own one yet but am considering a very clean 94 3/4 ton,ext. cab with a 4l80e and3.73 rearend it is also 2wd.The main reason for considering this truck is fuel economy,I have owned ford powerstrokes in the past and was not all that impressed with the economy of this engine,I averaged about 14mpg. Would the above mentioned chevy get better milage and if so what could I expect.thanks in advance.

That truck should get very close to 20mpg stock assuming everything is in good working order, unloaded. With some work, you could do better than 20.

Tire size and engine speed (RPM's) will have alot to do to determine your final numbers.

Thanks guys,tires appear to be in the 245/235 16 range but I'm not sure.20mpg. would be amazing.Right now i'm driving an 89 4x4 sub with 4.88s and 35in tires,I have overdrive but I would be suprised if i do better than 12 or 13 on the highway.I may need to buy that truck.

89 sub? 350 right? if you had a 454 you would be lucky to get 10 with those tires/gears.

If the truck needs tires, put 265 or 285/75/16s on it and you'll get a little better mileage with those gears, 3.42 would be best, but O/S tires will help compensate.
Keep in mind it may need some maintainence related work to get 20, and performance mods to get over that.