1963 Plymouth Valiant Trunk Lock jammed

Gday to all.
I have a '63 Valiant 'vert with the trunk lock jammed and not wanting to open.
The car was brought over to Australia many years ago and the key worked for most of the time that I have had the car.
Unfortunately I haven't been able to open the trunk for about 2 years (I hope that my lunch wasn't in there).:rolleyes:

I have decided to attempt to get it open.
The Aussie Valiants in '63 used a different lock (I'm thinking maybe like the later A bodies?).
I have read a couple of threads re '63 locks, but couldn't see anything with a definitive answer - except spending a forune on NOS ( if it can be found)..
Can someone give me a quick rundown on my options please? - (short of selling the car - ha).:thankyou:
Gary
Gary,
Remove the rear seat cushions (first the lower) then 2 bolts to remove the upper. Then reach thru from inside thru the rear seat brace with a long flat blade screw driver(30 inches or longer) and turn the center of the trunk latch 1/4 turn to your left!