Yes a spring is missing. Goes in the circle part with the bolt in it.
I've pondered that. I just thought they designed the hood so that when you drove down the highway, it would catch enough air to lift at around 30 miles an hour.
Ask me how I know.
I'm no expert but my 70 latch didn't look like that. It looked like the one on the very first post. ( also had chunks of hair, scalp and blood on it from multiple encounters with my head too! 
)
May be one of the benefits of being short, I don't often hit my head on low hanging fixures.
Just had the lever not the "pull rod" ?
I don't have any info that would indicate the hood was changed out on my car. Mine was a pretty late build in 70, so maybe it got the updated version. I'm going to take a closer look. It could be that the previous owner changed it out for a later repop variety
The bottom latch on mine is the same as yours though.
I took them all off when I went to the T/A hood.... my scalp smiled that day! 
If you still need the spring I think I still have it somewhere, the rest of the latches I gave away to members.
Appreciate the offer of the spring. Don't go out of your way. But if you do find it, let me know. I suspect there was a spring there at one time after the restoration, but maybe it departed energetically one day.
