Doesnt matter if it was a 6pk engine or not now,It is only good for the matching numbers car. The 69 70 and 71 are the most desireable years to have. The heads you have I guess you know by now are not original to the engine. They are closed chambered, but I cant see the numbers. Looks like 516's by the size of the valves, which by the way need to be thrown away. Look how far down they are sunken into the seats. Heavy rods blocks are a thing of the past, but It would be worth quite a bit to the right person. But not enough info. I would even trade you my 68 running 440 block for your 70 block, just to have the right year. But really, you dont have a bunch there unless you can say what internals come with it.