99 Silverado 1500 Shock Swap!

I have a 99 silverado. I recently recieved shocks out of a 2500 crew cab 2004 model (don't think its a hd). My truck has around 93,000 miles and started riding rough litte bumps and pot holes just slam the truck don't remember it being this bad could be tire softness. But I want the 3/4 ton shocks on my truck they look identical in length and size will they fit; these shocks have around 30,000 on them. Help please before i tear into it!