If you ever wonder if they are rare, then no. They are simply all sitting in someone's garage.
How do I say that with certainty? Well, look around. They sure as hell ain't driving anything with a hemi to work anymore. They've all been collected, or they've been sitting in museums. Sort of a shame, to desire a speed part so much that it won't get used ever again.
That's just ironic. Buying up hemis to take them off the road. In these 2 photos along you're looking at about 10 hemis without cars. Probably from either blowing the motors up, or wrecking the cars.
But, you aren't looking at 10 cars with hemis, ready to go out and play, have fun, and make smoky burnouts. Damn shame.
Top photo from https://www.facebook.com/groups/1686223568321025/permalink/2105500493059995/ in Pennsylvania. Bottom photo I took in the hills north of Honolulu back around 1992 or 3