What I did on a 1965 Mustang was adapt a universal cable lock.
These locks have a locking button that mounts inside the car. The other end is a cable with a pin on it that slides in and out of the cable
You are supposed to mount the end of the cable onto the radiator support with a bracket. Another bracket mounts to the underside of the hood. When you push the locking button in, the pin on the end of the cable slides into the hood bracket, which locks the hood down to the bracket on the support.
But I didn't want any of that crap mounted on the hood or support, so I eliminated the brackets. I drilled a hole in the side of the hood latch mechanism and mounted the end of the cable in the bracket. I drilled another hole in the part of the hood latch the moves forward when you pull on the lever. Now, when the locking button is pushed, and the pin on the end of the cable moves out, the pin goes through the hole on the release lever and keeps it from moving. If the release lever can't move forward, it won't release the hood.
With this adaptation, there are no obvious brackets to mount. In fact, other than the cable running from the headlamp cavity to the latch, you can't see the lock setup at all. With a black cable, it is hard to see it even when you look for it.