I can only speak from my own experience with a '50 3100 4 speed. It did have a rear tranny cross member, but it also had a torque tube rear end that I believe was the basis for the rear cross member. In about 1978 I replaced the rear end with an open drive line and ditched the cross member. In 30 years I have not had any problems here. I will let you know if I do in the future.
