The original torque tube springs have the mounting pins moved about an inch and a half forward to compensate for the pivot offset of the rear end. The 55 1st series springs have the mounting pin location dead center as they are set up for the open driveshaft rear end that does not have that offset. I think if you turn the springs, you will actually move the rear end back closer to 3 inches instead of the 1 1/2 that you want. Again, if you still use the torque tube rear end, whatever distance that you move the rear end back, you will lose in spline engagement on the u-joint at the transmission. Personally, I don't think you have that much room to give up. As much of this has mentioned, this is really my opinion but when my truck had the 55 1st springs on it with the torque tube rear end, the wheels were centered in the opening but I felt like it looked "silly". It could just be what I am used to. To each their own. My biggest concern would still be the spline engagement.
