If the price is right and the engine runs while it might not be origional to the car it might be worth it.
Pull a plug and shine some light in and you should be able to see the hump on the piston.
Also look at the punches under the drivers side head for year etc.
Also if the heads are older pre 66??? the manifold bolts will have a smaller head on them than the 66??? Up heads. ( There is also an angle difference and some casting line that is also a tell for old heads. IIRC) As I understand it the older head engines are not as desirable due to intake availability.