On my Olds I bought last year with no keys, I took the back seat out and taped a flathead screwdriver to the end of a broom handle and aimed for the little slot on the backside of the latch. Helps to have someone hold a flashlight. Worked like a charm.
Or......................you could use a slide hammer and never need a key again!!!!!!!!!!!!!!!!!! They are good for junk yard cars too where's there is never any key.
The way I got my 61 trunk open was to get one of the neighborhood kids, show him how to unlock it from another car I have, took the backseat out and had him crawl in with a flashlight.