I was concerned about removing the cross member on my '50 3600 for all the reasons discussed. I am using an NV3500 transmission so not the same but the same problem as my transmission have a full bell housing and an external clutch slave that further interferred with the cross member when I located my SBC engine where I wanted it (as close to the firewall as possible).
I made vertical cuts in the cross member inboard of the frame on both sides, welded plates to the remaining portions that remain rivited to the frame, and then attached plates to the removed center section that allowed the center to be moved down and back.
I needed to modify the transmission clearance in the cab to clear the transmission bell housing and fabricate a different transmission cover.
