Both the Montreal and the Duetto have the same 4X108 bolt circle. The Montreal brake calipers hit the inside of the Delta Milano wheels -due to the architecture of the wheel. For the record, I've never seen Delta Milano and Turbino used in the same description; unless it was contrasting the stock 'Turbino' wheel to a design, such as the Milano. When I bought my wheels, from Italy, they were identified as "R.B. Milano" wheels; I haven't seen that description again since.
The Delta wheels require about 15 mm of spacers between the Montreal hub and the wheel -in order to provide clearance for the calipers. This leaves about the bare minimum number of exposed wheel stud threads (7 or 8 I think).
I experimented with 24 mm thick, 4X108 to 4X108 adapters. This presented another set of issues, in that the adapters are installed on the wheel hub, using 'internal' thinner and smaller diameter lug nuts. These nuts are inside a machined 'lug' pocket in the 24 mm thickness between the hub and the wheel. The adapters I purchased came with all 'internal Right Hand Thread' lug nuts. Unfortunately the left side of the Montreal uses 'Left Hand Thread' lug nuts. No LHT lug nuts were available in a thinner and smaller nut size. Standard LHT lug nuts can't be tightened inside the lug pockets, even with a thin walled socket. In retrospect it might have been easier to hog out the lug pockets to a larger size but the nuts would still need to be shortened to fit.
Fortunately, a friend and club member who is a very skilled machinist, was willing and able to machine a beautiful set of smaller LHT nuts from my Duetto and a few from his own collection. Eventually it was determined that the 24 mm studs that came on the wheel adapters, were also too short for the Delta alloy wheels. The short studs required replacement with longer 35 mm studs.
In a nutshell, this entire project became just another expensive exercise in Alfa self-flagellation. I've seen other 105 cars with the Delta Milano wheels and suspect they just 'bolt on' the Spider and GTV but I haven't tried.
Mark