leaf spring relocation question

I am getting ready to relocate my leaf springs and do a mini tub on my Darts. I have a question about mounting the front spring perch boxes. I have seen the rear frame notched out on the inside, the outside and cutout completely. Do the boxes get welded to the insides of the frame, the outsides or cutout completely and welded right in the middle of the frame? Or cutout completely and welded offset to the inside of the frames so that the outside of the box matches the outside of the frame rails? I have looked at a lot of pics and have seen it done many ways. Just worried about front to rear alignment of the leaf springs.

Any clear pics would be helpful too. Thanks.