So, let's say I wanted a 180 on the rear..

[Moronic]

Just on the handling thing ...

In my small experience the effect of widening the rear tyre is not just a matter of slower turn-in, tho that is obviously very relevant.

There's also the greater reaction from the steering to bumps and seams in the road surface, and some loss of steering precision even on a smooth surface, and a greater need to get your weight inside the bike for neutral steering in turns.

The wider the tyre, the further from the bike's centreline the edge of the tyre is.

That means bumps or seams hit off-centre can exert more twisting leverage on the bike.

And it means the tyre contact patch migrates further away from the bike's centreline as you lean - so you have to get further inboard to keep her balanced.

The difference in feel can be quite pronounced even going from a 180 to a 170, IMO. The bigger tyres offer better grip under power, but it ain't cost free.

[junior varsity]

And you'll see none of that benefit unless you have a big ol' motor. 170 is plenty of rubber.

[A.duc.H.duc.]

So for the sake of clarity, and I guess redundancy. All you need for a swap to a 5.5" rear is.
Wheel, cush drive, and the spacers?

I'd like to say yes absolutely, but you know things vary from bike to bike sometimes with ducatis. What I can say is I got a 900SS 5.5 inch rear with the cush drive and spacers. Took those parts and some of my origional parts, and it works on my '97 750.

You should not need any custom parts to make it fit.

Justin