the best method for swapping triples

[Speeddog]

There was a video on YouTube where some guys went through the whole deal, replacing the head bearings too.
Wasn't on a Duc, but IIRC they got it all done correctly.
Think it was from England.

Keep in mind that on a rearstand and a jack under the motor, it's a bit tippy if you manhandle it.

Better with a rearstand, jackstands and a pipe under the horizontal cylinder.
Put a folded shoprag over the pipe to avoid scratching the cylinder.