There is a way using configuration files on both ends to change this, if necessary, but those 37890-37892 ports outbound are actually static and you will still need at least 1 of them (as Curtis mentioned, you can close 37890 after initial connection, and it's unlikely you'll see 37891).
The ports that will be used to connect to 37890-37892 are also fixed and in a configuration file, in case you need to change the initiating end.