Cooter Tech

I am installing a t-56 into my 78. I wrote the dimensions that were with my 4 speed transmission at the out put shaft, such as driver side to centerline etc. The dimensions with the t-56 are not even close. Does anyone have any information as to what the dimensions should be at the out put shaft with a t-56? Is ther a way to check that it is properly centered with the rear end?