Installing in the factory looms makes for the best, but it is painstaking work. Personally, I've done 2, my first car and my cousins. I don't think I will ever do that again even if someone pays me. Another, almost as good way is to make your wiring look like the factory looms. Get the same type of loom that is used by the manufacturer of your particular car and camoflauge your wires. Don't just ziptie your wires to existing looms either make it look the same. Since you have an older car, you may want to clean/retape some of the existing wires so the new wires you put in don't stick out.
Other good places for the alarm module up behind the instument panel or above the glove box. It should be hard for you to get to.
