unless something fails I don't see why you would need new rod and pistons. Unless you want to just throw money at it, or have dyno evidence showing that you are loosing a substanical amount of hp. I would leave it alone.

If there is something wrong with it, do the typical compression, leak down tests and work from there.

However if you feel un-comfortable about the motor, then pull it apart and measure every single thing prior to removing it and compare it to whatever to set/speced it to when you built it.

Also depending on when it was built the aftermarket and capabilities have increased ever so slightly so you could make jstu a little bit more power with a new rebuilt engine utilizing the new technology. Whether or not that is allowed in the class for said engine is another thing entirely.