Good day all, I have made some good progress over the last few week son my 350 build, and tonight while installing the valve springs I was looking over the new heads closely and noticed eh center coolant passages. Then I started searching the site, then i felt ill after reading (that I may not be bale to use my new heads). It seems 72 was the change over year. the original heads have a 73 casting on the exhaust port but i don't have the casting numbers with me at the moment. The new heads are a 3452 casting. I have included pictures of the heads (both) and block. It looks like the gasket and block material will cover the center coolant port. Let me know that you all think. Thanks, Mike