I have a 1982 C25 probably just like yours. My charger is in the cockpit storage compartment on the port side. There is lots of room so heat isn't a problem and my shorepower connections are in the same place. You will need to run wire into the cabin where the batteries are located. Make sure you size the wire large enough to handle the amps the charger puts out. There may already be wires in place from previous owners.
Congratulations you will like your new boat
TJ Portland too