I'm not big on the frame clip personally. Cutting and welding the frame together is just one small part of the project, cutting inner fenders and making bumper brackets up and the worse part the rad support are all more than the frame if you ask me. That Monte is a better choice than the popular Camaro being it's narrower by a few inches, makes a BIG difference.
What is stopping you from getting one of the many kits to put a Mustang II type front end on it? If it's the money, think about that again, rebuilding Monte, replacing the leaking steering box with rebuilt, all the metal needed, etc. The kit isn't that much when you add it all up. They have all kinds of rear leafs that simply bolt in that improve that old trucks ride too.
Think about it, but here is some study for you on doing the graft you have planned.