Want the low buck solution? Back when I had my '72 Malibu ragtop, I had the same concern-outside hood latch, any yo-yo at my high school could get under the hood and monkey around. Anyway, I noticed a '68 Malibu at a cruise night and he bolted a medium thickness chain to his hood latch. It was long enough to pass down between the grille and rad and padlock onto a factory hole in the frame. Paint it flat black and no one will even see it back there.
On the other hand, I guess this may require mods to your upper grille/rad cover, so why not go whole hog and just adapt a cable operated latch? I remember a lot of guys used to use VW Rabbit ones with some sucess. Prowl the boneyards and look for "small cars" cuz the latch should fit better. Best of luck and please let us know how it works out.
Regards,
Wannabe
