The stock wire was supposed to be good for 55 amps, so it will handle up to a 60 amp fine.
You have 2 choices in the change out, (1) buy the model that replaces the lower converter section of the electric panel, or (2) if you have the space near the panel, get the PD 9260, which is the "stand alone" model, and leave the Wfco where it is. Just transfer the 120v ac input power from the Wfco, to the PD, and connect a pos and neg cable to it, that's it.
That's what I did, left my single stage slow charging 7300 right where it was.
There would be no advantage to going w/ a larger converter, unless you plan on a larger batt bank in the future.