I have 2 and use both or either. I started with a gun cable lock, the hood will open just enough to get the key in and it hangs from the hood on the '67. I looped it through the hood part and lock it around the grill part where the hood latches.
The other is a cabinet lock that I drilled a hole for, the tumbler tab keeps the lever from moving to unlatch the hood. I can just get the key to it to unlock. Got this idea from another forum, this is his pic I saved. I used a cabinet lock from HD but will replace with a stronger one from a locksmith or cabinet co. as this one is China cheap.