I agree with spike that just running the event will bring him on loads. The 300+100 (off 60sec?) was a good indicator for what he did a few days later. Other options are 250m/120m, 200m/200m whic will all be race replication runs/specific endurance.
There is also some information regarding 200m times versus 400m times and being able to do your 400m in 200m best x 2.20 will be a good bench mark performance. Going under that requires a bit more endurance quality.