There was a rear-of-transmission cross-member through 1953 (for all transmissions).

The rear-engine-mount cross-member changed in 1954. Its "stronger" design allowed the elimination of the rear-of-transmission cross-member on all drive-trains, except for the very heavy Hydra-Matic transmission.

What is the weight of the M-20 transmission?
Maybe someone knows the weight of the 1947 3-speed transmission?