I'm pretty sure Loz at AB has fitted either a Q2 or Quaiffe to a 145 t - spark.
The gearbox did have to come apart but it is possible as far as I'm aware but I'm sure he'll be along before long too confirm or deny.
I think some people are slightly missing the point here
A Q2 diff is an Alfa built differential which was a basic copy of the Quaife ATB diff which was fitted to GT diesels and the for of the Q2 model that came out in 2007. We thought is was a great improvement and had a go at fitting one in a GTA, it fitted and worked well so then on the best mod for a GTA
Quaife is a brand name and they make many many different differentials and gearbox components for mostly race applications. We stock there product over the Q2 as it is a far superior bit of kit.
The Quaife diffs we stock fit the following Alfa's
QDH2K for Twin Spark application and gear box needs to be removed and completely stripped to fit
QDH6E for Busso V6 and most diesel applications, this can be fitted without removing the gearbox from the vehicle (this is the one that is most similar the Q2 and has the same application)
QDF21B for the F40 gearbox found in the 2.4 159 & Brera etc, this gearbox needs to be removed and completely stripped to fit
QDF25B for M32 gearbox found in 159 1.9 & petrol turbo, Mito 155 etc, easiest to fit, again no need to remove gearbox from vehicle
We are currently working with Quaife to develop QDH7E for the C635 gearbox found in Giulietta and late Mito etc, this will be available in a month or so. This will involve removing the gearbox from the car and complete strip down. This gearboxes have an inherent design flaw which we are also working on