If you actually want a better ride I would not recommend any on the shelf spring. The leaf packs are short on these old trucks. Here is a thread in the Blazer section to take a look at
https://67-72chevytrucks.com/vboard/...d.php?t=801644 Personally I would stay away from any gas charged shocks as well, unless you are doing some hard fast off roading. They will just make the ride firm. The Bilstein 5100's may be okay with a soft spring. A twin tube Hydraulic will be fine for everyday use and offer a much better ride. There is a reason I am putting 99+ type leafs on the back of my K10 as they are a foot longer. I am also using Deavers which use more thinner leafs than a traditional spring. Atlas leafs are made the same. If staying with the stock hangers and you truly want to improve the ride check out the thread I pointed out. Nice leaf packs will cost a bit but you will not be sorry. Addtionally, polly bushings will tighten up suspension/handling but will also transmit more into the vehicle. Looks like maybe a 4" lift on the truck. Look at the blocks in the back. If they are about 2.5'-3" it is a 4" lift.