Hi, I am a professional certified mechanic, with an engineering background, and 35+ years experience. I will do my best to assist you. Also keep in mind I don't know if you are a pro or a novice, so feel free to add any additional info at any time.
I saw that, the billet hinges you have if they are specific the the 69 Chevelle, everything I previously said applies. It isn't that they absolutely cant be installed, it is that it might take 20 to 40 hours and be obscenely expensive is my warning. There is also no guarantee that after all of that they will work satisfactory. I do a lot of custom work, and I have a machine shop/prototype shop at my disposable, and I still wouldn't try this. Hood hinges are so finicky. They have to be perfect to allow the hood to open properly. They have to pivot without hitting the fenders, grille windshield, and more. It also has to latch, and stay open correctly, so there are a lot of potential issues to look at. It might help to look at some pics of the geometry of the hinges. link HERE
is a link for a 69 Chevelle, and link HERE
is a link for a 69 cutlass. The Chevelle hinge is 1969 only, the Cutlass fits 69 to 1972. Look at the base length, mounting, arms, and spring location. They pivot/rock to open the hood in a completely different way. The Cutlass hood is also heavier too, and will require a stiffer spring that fits the hood weight/shape of the hings. Go over all of this and if you have any more questions at all, I am here to help. Good luck with it, have a great day, and Thanks for using Just Answer. I do not get paid for my work unless you rate at 3 to 5 Smiley Faces or Stars, a bonus is always greatly appreciated. If the answer is not clear, let me know what additional help you need, and I will be happy to assist you further.