SELECT 
    CASE Model 
       WHEN 'Mountain-100' THEN 'M200' 
       WHEN 'Road-150'     THEN 'R250' 
       WHEN 'Road-650'     THEN 'R750' 
       WHEN 'Touring-1000' THEN 'T1000' 
       ELSE LEFT(Model, 1) + Right(Model, 3) 
    END + ' ' + Region AS ModelRegion 
   ,(CONVERT(int, CalendarYear) * 100) + CONVERT(int, Month) AS TimeIndex 
   ,SUM(Quantity ) AS Quantity 
   ,SUM(Amount)    AS Amount
   ,CalendarYear
   ,Month
   ,dbo.udfbuildiso8601date (CalendarYear, Month, 25) AS ReportingDate
FROM 
   dbo.vDMPrep 
WHERE 
   Model IN ('Mountain-100', 'Mountain-200', 'Road-150', 'Road-250', 'Road-650', 'Road-750', 'Touring-1000') 
GROUP BY 
    CASE Model 
       WHEN 'Mountain-100' THEN 'M200' 
       WHEN 'Road-150'     THEN 'R250' 
       WHEN 'Road-650'     THEN 'R750' 
       WHEN 'Touring-1000' THEN 'T1000' 
       ELSE LEFT(Model, 1) + Right(Model, 3) 
    END + ' ' + Region
   ,(CONVERT(int, CalendarYear) * 100) + CONVERT(int, Month)
   ,CalendarYear
   ,Month
   ,dbo.udfbuildiso8601date (CalendarYear, Month, 25)