Unless you understand very complex algorithms for winning the lottery, you are probably not going to find an Eagle with a manual transmission. It is difficult enough to find one that works. Note I'm not talking about finding one that doesn't have any issues, just...Runs.
There is no interchange catalog for this car and everyone avoids it. For whatever reason, you end up with an unsolvable problem if you rely entirely on parts guides and books. The parts are all there, but no one ever lists product compatibility with this particular car. If you're used to threading camera film into bath cylinders in a pitch black room, you might be pretty good at figuring this one out.
The range of backwards and future compatibility between other makes and models is astonishing. It's unlike any other vehicle but it still retains its identity and some rather unique problems along the way. Almost all of them stemming from neglect. This is a thing.
When you finally get an Eagle, examine it carefully. Figure out what's good, what's bad, what works, what doesn't and what needs to be thrown out. It's especially important that you figure out what you might need to work on later. If you have a place to do a full store and disassemble, it's usually easiest to take out the drivetrain first and rebuild one section at a time. It isn't difficult, but it is time consuming and somewhat expensive. Eagles are usually project cars because so many of them just sit for so long. There really doesn't appear to be any absolute reason for this collective behavior either. Previous owners just didn't give these cars very much attention or they gave it way too much attention trying to fix one problem and gave up out of frustration. It's been over 30 years since these cars were made, they're unbelievably easy to maintain but you are going to be the only one that really understands your Eagle. It's a lot to take in and God help you if you already have experience as a mechanic from wrenching around on other vehicles. It all becomes a major conscious roadblock instead of genuine help. Unfortunately, this is the hardest thing to explain to new owners because it's something you have to experience on your own.