[Daves55Sedan]

In those days, it was not unusual to see a 223 cu in I-block 6cyl engine in trucks with manual transmission.
1954/55/56 223 truck engines would have been nearly identical.
Y-block bellhousings will not mount to the 6 cyl engine. The 6 cyl has a smaller bellhousing clutch and flywheel than the Y-block.
You cannot use a bellhousing from a car on a pickup truck because the truck bellhousing has tabs in the casting for transmission mounting to the truck frame.
But if it was me, I would stick with the Y-block. The '54 F100 would have had a 239 Y-block which is an animal all its own and not many interchangeable parts with later Y-blocks. But 272, 292 or 312 Y-blocks have many interchangeable parts and lots more availability of replacement parts.
Not sure if a 239 bellhousing will fit a later Y-block though???
Exhaust is run on the opposite frame rail if swapping from a V8 to a 6cyl and a different exhaust header will need to be made. Some clutch linkage may need to be re-worked. Carburator linkage will need to be swapped from the 6cyl. You will need to transition to a smaller intake hose size for the radiator somehow with a reducer or swap to a 6cyl radiator.