why not pick one up at a thrift shop.
Actually there is an answer to that, only not a great one.
The later the model, the smaller the circuitry.
1970: 12+- boards 1980: 2~3 boards, 1990: 1~2,
Then the boards start shrinking inside the case.
What I really want is just the tuner, or a real small thing.
John A.