What is your rear gear ratio? T-5's come in different overdrive gear sets to work best with whatever rear gear ratio you already have. There are different length tail shafts available for T-5's, But you would be real lucky to find one that would be exactly the same total length as what you are replacing. Hopefully someone will come along in here who has done exactly what you are trying to do and save you a lot of head scratching and parts scrounging.
Carl

1952 5-window - return to "as built" condition | 1950 3100 with a 235 and a T-5 transmission