My propane tanks are located in small lockers aft of the cockpit lockers p&s next to the transom. D0 you have those lockers? They have a scupper at the bottom of each locker to drain the heavier than air propane gas overboard should there be a leak. Otherwise you will have to build a storage compartment which will drain overboard and only overboard.
There is a switch in the galley for a solonoid operated valve in the propane locker as well as a manual valve on the tank. (The other locker is used for a spare tank.) Also the circuit which energizes the solonoid has its own breaker on the breaker panel.
Good luck with your 323. They're great little ships. If you need pics let me know. It might take a while, but glad to oblige.