Interesting thread. I have not yet had the time to do anything with either of my recently acquired '53s, but I have one Hydramatic car and one three speed manual car. It was said above that the crankshaft is different on the manual trans vs. the automatic - Is this just a minor pilot bushing issue, or a fundamental difference that cannot be corrected easily or at all with the engine assembled?
In regard to the above, the T5 is a manual transmission, so it would seem that acquiring a hydramatic car/parts would not help in that swap.
I continue to contemplate what to do with the drivetrains in my cars. I thought about swapping the hydramatic over from my parts car to the existing manual trans car, but it sounds like I may be swapping the entire engine/trans assembly if I want to make that happen(along with all the other incidentals like the steering column, pedal assembly, etc.).
All that said, I wish I had some advice to offer on the T5 swap, but I'd be very curious to learn whether or not that swap is realistically feasible. I could see that being a very worthwhile upgrade, making the car substantially more daily drivable.