Personally none of these are a "got to have it" for me. The Opal GT is a very very sweet car, BUT the proportions are just a little odd, If I had to choose an entry level 2 seat sportscar from the early 70's I would go for a Datsun 240Z/260Z instead.
The Type 75 Lotus is probably my first choice out of the group. Although it is something I have never heard of until now.
The Mazda & Wagoneer I have no interest in for being collectable, using anything with 4 doors for something other than utility is off my list.
The Mercury Monteray, looks like someone at Mercury wanted to see how long they could possibly make a car and still be legal... It is not unattractive, just seems like it needed another couple of weeks on the drawing board.
The Cougar XR-7, I find these to be stylish, these have a lot of potential honestly.
The Dart Hang 10, is in the throws of the smogged out era of vehicles. Styling was hampered by regulations, they were under powered and designed to be more efficient because of the fuel crisis. A 707hp Hellcat engine would be too much, but for me to be enjoyable and more interesting is maybe a new 492 Hemi under the hood.