I do not think it possible to do 2,000 in 48 without doing 1,000 in at least one of the two 24-hour periods. If you only did 999 miles in the first 24, you would necessarily do 1,001 in the second.
That said, an SS1k & BBS are separable as are a BBS & SS2k. You can do one without the other in each pair.