As far as i can remember,up to FL290 -vert.separation is 1000' for opposite direction traffic,and 2000' for same direction traffic.
eastbound levels are 250(the lowest ,as you said),270 and 290
westbound levels are 260 and 280.
Above FL290 is (was) "increased" vertical separation ,so now it's 2000' for opposite direction traffic and 4000' for same direction traffic .
eastbound levels are(were) 330,370, 410...etc
westbound levels are (were) 310,350,390,430...etc
regards