Append Three VARCHAR(MAX) variables

DECLARE @FileBody1         VARCHAR(max)
            ,@FileBody2         VARCHAR(max)
            ,@FileBody3         VARCHAR(max)
            ,@StartingIndex     INT
            ,@FileLength        INT


    SET @StartingIndex = 1
    SELECT  @FileLength = DATALENGTH(DC.FileBody) FROM Configuration DC WHERE DC.ID = 1
    SELECT @FileBody1 = SUBSTRING(DC.FileBody,@StartingIndex,8000)FROM Configuration DC WHERE DC.ID = 1
    SET @StartingIndex = @StartingIndex + 8000
    SELECT @FileBody2 = SUBSTRING(DC.FileBody,@StartingIndex,8000) FROM Configuration DC WHERE DC.ID = 1
    SET @StartingIndex = @StartingIndex + 8000
    SELECT @FileBody3 = SUBSTRING(DC.FileBody,@StartingIndex,8000) FROM Configuration DC WHERE DC.ID = 1

select @FileBody1+''+@FileBody2+''+@FileBody3