I fancy this little mount every time I drive past! Looksike a great wild climb. Cool to see some interest here.
I don't have a topo but recall checking out North Brother, the BNT passes through there but brief exploration from the carpark suggests it would be nicely overgrown so an off track experience

Coorabahk NP just inland from Johns River is worth a look too. Have only driven the circuit through thus far. Nice little horseshoe falls, stripped state forest, views west of very old volcanic plugs amongst farmland, the Comboyne plateau and you can scramble up Big Nellie!
Think there is a free campsite on the southern way in, country showground type of place.