well except the leaf springs mounts would hang well below the frame if you moved them forward. they are tucked up in a raised section right now.
you are not cutting a frame in half, well except the part of the rail you are shortening. the splice is where the two frame halves are joined, every s10 has the same front section and the rear section is identical to every wheelbase except for the length. this is literally how the factory makes the different wheelbases, you simply grind off the factory weld (after making yourself some reference marks of course), slide the two sections apart, cut off the excess, and slide back together and reweld the splice.
its less work than even cutting 5 inches out of the flat part of the frame.