5 x 1000 in 3:10, 400 (2 min. tops) rest.
You can build up to this by doing 3 x 1000 the first time out, or doing a longer rest (no longer than 3 minutes though) but in 6 weeks you need to be there-
5 reps total in 23 minutes total, from the start of the first 1000 to the end of the 5th.