i just use old holden keys or any other key that will go in the lock to jiggle the lockable caps..i have not needed to drill one or butcher one off for 20 years..
good luck with the tank and the filters if its been sitting that long..i would pull the tank and clean it..at worse run a few filters and see how much crap comes through..it wont hurt the motor but will not do the carb much good..
pullin the tank isnt that major..hardest part is getting the hoses off...