I would like to do the swap to my 81 half ton that i just bought from a guy in Arkansas. He had put 4" blocks and longer shackles on the front. I dont beleive they are safe as well as anybody else. My question is do the springs have to come from a 4x4 or 2wd. This mod is something new to me. I was just going to buy springs from BDS or Tuff Country but i saw the mod and it intested me. Any help would be appreciated.