gearbox bolt

[VL Berlina 5speed]

whats the best way to get the gearbox filler bolt off?
its that dam square shape bolt and is 16mm or so

the car isnt a runner so i cant warm it up.
ive had vise grips on it and with all my force and pushing against the K frame it wont budge, hammer n spanner = no luck

not enough room to get a long bar on it for leverage

need to get it off as there is no fluid in the box from when it was out

any tips ideas would be great

[wildss]

end of an extension? im guesing either 3/8 or half inch

[jatsvl]

it may have lock tight on it as you probably are aware do you have access to a small propane torch to heat it up? or a stilsens (plumbers) wrench a 2-3 inch one would make it much easier as they are heavy. also if you can jack the car up onto stands you should have enough room for a lever bar about 1-2 foot long.