Scott made the turn in close to world record pace and held on to break his own previous best of 1:44.91 by half a second, with Dean in hot pursuit.
Matthew Richards, James Guy and Calum Jarvis also achieved the Tokyo qualification time in a race that bodes well for the men's 4x200m freestyle prospects in the Japanese capital.
"I'm delighted with the time, but just to get the win in that sort of field is really good," said Scott, who also equalled his British best in the 100m freestyle earlier in the week.
Sarah Vasey also went under the Tokyo time as she won the women's 100m breaststroke, finishing in a lifetime best and just 0.03 seconds off Siobhan-Marie O'Connor's British record, with Molly Renshaw also achieving the mark.
Daniel Jervis made up for missing out on the 800m mark earlier in the week by roaring home in the men's 1500m freestyle, touching more than four seconds inside the 14:55.91 consideration mark.