IIRC, you could get a 290, a 343 a 360, or a 390; all with either a Auto or Manual. I believe you could order a 401, not sure. It's not on the wiki, but a book about AMCs had the engine listed in there. So I'm not sure on the 401.
That sucks you passed up on so many legendary cars! It was probably just like looking a Camry, you see them everywhere, they're not special.. little did you know! The Cuda sounds amazing. I wished I could've had that car. Was it a 67 or 68? I can't remember when they switched the body style, 69 or 70...
I wish AMC was still around, even though they did bring the Pacer into the world... eesh.