I have not looked at an S10 chassis before. It seems all wrong to splice a frame from the factory. It seems weak with a vertical weld splice. I see it has a boxed section in front that transitions to C. It seems like the swoosh and box section should be on the other side of the splice (run past the vert weld). Weird. I have not seen this splice in person but it is counter to everything I think, have seen and read about splicing a frame for shortening, lengthening, etc.
I asked because I missed that you said "factory splice", was looking for a fish plate on the outside and thought it was an unfinished splice job. As you say, it works.
