I have a 69 Z28 with the original motor but the wrong heads and I want to put the correct dated heads on my engine. I have a set of 186 heads, both dated G 29 9 , my friend has just bought a 010 block that has a set of 186 heads both dated H 18 9. My cars motor is dated August 25th on the engine pad. What would be a better date head for the car? Would the G 29 heads work or should I try to use his H 18 heads?