The motor has been sitting for years now so what shape are the seals in, rings stuck to bore and all the other things that happen to motors that sit. The carbs and manifolds were where all the value was.
It could be an A12A being a later motor in the U.S.A. but its value isn't great. They have had the motor up for sale on and off three years with no takers. Even at $400 I think one would be hard pressed to get any takers, A12s are rather unloved and usually anyone who needs a motor goes bigger.
I think it is like my 80s motorcycle brochures, cool to but not worth much.

Tom