I feel the pain that you may be about to go through as automotive springs can be a real buggar to get spec'd and spec'd right. I would start with Eaton Detroit Spring's phone number. They have 4 styles listed for your truck with the actual weights listed too. That weight may be all you need to determine what you have, but I have found them to be pretty helpful in determining what you have on your truck and what might happen to your ride height if you change styles. Go here...
http://www.eatondetroitspring.com/find/
and fill out the search info to see what they offer along with the spring weights, then give them a call and talk springs. They seem to be open with the specific spring data (like # and diameter of coils, diameter of the steel, overall unloaded height and so on). Even if you do not buy from them, you will likely learn something useful. Keep in mind that springs on any car can be a lesson in patience AND opening your wallet. It took 2 sets of rear springs and a set of front spacers for a recent F@rd project before I got the ride and height the way I wanted. Also, new springs will ride higher than your old wore out springs. Good Luck!