There is no ‘good’ only ‘appropriate’. This depends on the athlete of course, but given a good lead up (GPP/SPP weights programs), you could go with something like this:
Snatch (if you can do them safely) 2 (80%x1rm), 2, 1 (90%) - med ball ceiling throws 6x5kg
Powerpull (Clean Pull) 2 (80%), 2, 1 (90%) - box jumps 2x3
RDL 3x5 (80%)
You might put bench press/bench pull or another leg exercise on another day if you feel you need it, or just use med ball work as your strength component for the day. Ultimately all you want to do is ‘top up’ the CNS if you haven’t already done that through your track work. IMO you do not need to lift a lot of weights as a 400m runner inseason, so long as you have built a decent base of strength in the pre-season. Keep in mind that weights are primarily of use to you in the first 20m of the race (5% of the 400m). Most of what you do will come out of your runs and drills, so make that the priority.