First of all...Plymouth built 135 Hemi 'birds...so you have twice as big a field to look through than you thought.
If I were in the market for a big-dollar musclecar...I'd wait. They are at incredibly over inflated prices now, and it won't be long before there is a correction(price drop).
Galen Govier is known as the authority on Mopars, but is also not infallable. And, with his help comes a hefty pricetag. There are many self proclaimed experts in the Moapr field, and most of them have something to sell.
I would scan Hemmings. Once you find a car you are interested in, contact me, and I can look up the VIN in a list I have that was makde when the 'birds came off the line new. This way, you will at least know if it's a real 'bird and not a clone.
There are many other things to check on a 'bird. Look for the VIN on the doorjamb sticker, VIN plate, data plate, engine and trans. Some were also stamped on the rad support. There much more to get into once you find a car.
Feel free to contact me if you need help. I restored two Superbird and know them well.