You may be able to tell a K Code engine from the outside. It has a different harmonic balancer. Pop a valve cover and see if the heads have the valve spring seats machined and screw in studs, although those can be 'faked'. The heads themselves should have two dots over the 289 cast in them. Once you tear it apart, you would see the connecting rod bolt differences. Are the exhaust manifolds still on and original? They are diferent also, but again, easily faked. Dual point diizzy? Again, easily faked, I have one if you want to buy it!