Spring Relocation Question

i follow what your saying,i just completed the same on a 69 dart and am helping currently on a 67 dart, and the answer is yes. The things to watch for is the taper in the frame, its wider in the front where you will weld in the box then it is in the back. Make sure the tube you weld in the rear is the same width as the spring, so your shackle bolts up square.Once your boxes are welded in, hang the springs and make sure the springs are parallel, and it will kind of show you where the tube needs to be welded. i think most of the offset is to the inside.Im probably not making much sense, but measure everything! As for moving the springs back one inch, i really dont think it will matter. i put my spring in the stock location and should have moved it back. both my 69 and the 67 have the rear shackle tube welded in the same location as the stock hanger would have it. it will just angle the shackle a little more on the 67.