This is a heck of a good question.
The big 265 flathead with Powerflite transmission was factory available in Chrysler Windsor in 1954 only.
The same engine was used in heavy Dodge trucks (W300) until 1962.
If these trucks were available with an automatic it would have been a 727 Torqueflite 3 speed 1957-62. Powerflite up to 56.
Was such a combination offered, and do any survive?
In Canada all Plymouths and Dodges used a 230 or 228 cu in version of that engine up to 1959.
In the US they used a different (smaller) block but I believe the trannies interchange??
So it should be possible to bolt up a Torqueflite using factory parts.
One thing that might mess things up. They changed the design of the crankshafts in about 1962 to use cap screws threaded into the crank flange instead of nuts and bolts. This resulted in a shorter crankshaft and different flywheel. Can you use a newer transmission with the old engine if you use the right flywheel/torque converter? I'm not sure.
The reason this is important is that they used a pushbutton transmission exclusively from 1957 to 1964.
This means if you want a gearshift that is compatible with the pre 55 car, you need a 65 or newer transmission - which uses a different crankshaft/flywheel/torque converter.
It would be very interesting if it were possible to mix and match different parts to put a Torqueflite behind a flathead 6 using all factory parts.
