I am not displeased with the unit I installed in my truck but I did retain the original (although modified for clearance) to provide structural support to the frame at the point where the rear mount for the front leaf springs. The cross member I retained was riveted in and may be in place on your frame (I cann't tell from the photos that you have provided).
In my case I do not believe that the original frame cross member I modified provided a transmission mount. I beleive it was used to support the bell housing but I do not recall for sure and apparently do not have any pictures of the original engine and transmission in place.
The cross member I added is only intended to provide a rear mounting point for the engine-transmission and not provide structural integrity to the frame.
