I went through the same thing putting an F10a into mine. The engine was from a type 3. It had a sealed bearing pressed into the flywheel unlike earlier motors with their spigot in the crank.
I've got a spare early input shaft so here's the difference. Sorry for the shitty pics, they're GoPro spec.
Old motor, early style input shaft. The splines are about 2mm in.

Late motor, early input.

This is the gearbox that came with the motor, it's from a type 2 and this is how they cut it down. I didn't get a pic of how I trimmed mine. I cut it about 15mm shorter and ground the ridge down.

Other than that, the late motor is a simple conversion.