There is no need to support the T-5 transmission. In fact, doing so may cause damage to this aluminum transmission case.
The front engine mount, and the two rear mounts at the bell housing is all that is needed to support your engine and transmission.
Adding a third support at the transmission tail housing is where the problem is.
Think of when you have a stick in your hands that you want to break on two. It is hard to do with only your two hands. Now, put your knee in the center of the stick as the third point and you will find that the stick will almost break itself.
So can your transmission with the third mounting point add in.
It would be a good idea to locate and install an original transmission crossmember to stiffen up the frame. Just don't attach the transmission to it.
Starting in 1954, these trucks no longer had a transmission crossover because the crossmember for the bell housing was redesigned and beefed up, negating the need for the transmission crossmember.
If the '54 and later truck came with either a 3 speed or a 4 speed, there was no support for the rear of the transmission.
Those transmissions weigh considerably more than a T-5 BTW.
