@Rog just keep watching auctions like Stout and Cabin Fever and the other regulars. For whatever reason I see them pop up in clusters for sale. These come screwed to a steel base and then in the regular rigid foam packaging. Too many breakable parts if shipped otherwise. My understanding of the (2-3-4) numbering, the numbers only indicate how many power units (plus 1) were in the consist. My purchase did not come with the other B unit. I also have a Great Northern Box Cab designated a Y1. 20-5526-1
Happy with mine - 20-5570-1 and it is happy where it is. ; )
Good Hunting ... Jeff