LOL! Richard no MP60 brother, go for the 40 that's plenty on a 46 gallon.

While I can't make an informed decision on the size you should have for an overflow, hopefully someone else can make a recommendation. I would highly recommend making a choice about a closed loop VS a Vortech before you start drilling. I personally prefer a Vortech but that's just IMO, I'm bias as I own a MP40.

Christopher