Loosen the clamp at the base of the column ,next to the gearbox, the
sleave will slide off the shaft into the passenger compartment. You may
have to remove some or all of the bolts holding the gearbox to the frame
or remove most and loosen the rest. So the shaft will be "flexible"
enough to manuveur the column out. Also the collars around the floor
where the steering column goes out have to be removed and of course the
shims and clamp under the dash.
To sum up.
1. Take the column out into the passenger compartment
2. It will slide off without removing the "bell".
3. You realize the skinny inner shaft will remain attached to the box.

I wonder why you thought the column had to go out thru the engine
comparment.