It sounds like the springs must be incorrect. I cannot imagine moving the hole in the frame for the rear shackle to bolt up! That would just be jury-rigging it to fit instead of solving the problem. Once installed, the hole in the spring leaf for the rear shackle should actually be a little past the center of the hole for the shackle in the frame. The rear shackle angle from the frame to the spring has to be angled back like in the attached photo so that the shackle can rotate forward on takeoff for the springs to work properly. If you bolt up your front hangers and jack the rear up, the rear shackles should fit relatively easily. If your shackle is laying all the way back and still is missing the hole by a 1/2", you have a problem with the length of the springs or the frame. Even if it bolted up, if the rear spring eye is in front of the mounting hole in the frame, the spring will be bouncing up into the frame when you go over bumps...I would start off with some measurements from the rear hole in the frame to the front spring hanger mounting flange and post the measurement here and someone will verify it for you. I will bet the springs are just not the right ones.