Hey 56, according to what I've seen advertised, the 1/2 ton ratio is usually 3.90 which can be changed to 3.38, 3.07, or even 2.78. I see 3.07 being more common and will probably work well for you if you plan on using it as a work truck still and should see you having no problems starting off with a load with 3.07s since you got a granny gear. This is what I remember seeing advertised for your type of truck, I looked it up again.
http://www.oldchevytrucks.biz/catalog2/0054.html
