For anyone thats interested, I just spoke with Ken from Oregon Cams regarding the 1970 340 core i sent him, he was honest and told me that he would not recommend re-grinding that core because of too much wear.
he did say that he had a more suitable core that we could use for the 68-4 speed re-grind, super nice guy and very down to earth.
re-grind fee $99
core fee $40