What is your 300 IH time?
Most likely you are an 800 runner. You won't actually be any good at it, but you won't listen to us if we tell you to become a miler.
Seriously, the question you have to ask yourself is how hard have I worked to run 50.6 and 23.X?
If you have never run year round, are more of a basketball player, or know your coaching is suspect the PSAC will certainly let you run the 400 even if you have to tell them you are thinking of moving up. If you were serious in the 6th grade, running year round and attending many track camps year after year to gain an edge, you could be topped out and need to look at longer distances.