Hi guys I am finding more out about my engine. I have a 75 c10 but the engine is a 327 ( punched to 331 ) I believe its a 1967 block. I got the number from the block but couldn't read the date code. the number is 3892657. I do know I haave the camel hump heads that DO NOT have the accessory bolt holes so i think they are the earlier ones. I'll get the numbers next week when I get the new valve cover gaskets in. Anyways in my attempt to learn more I am reading about lots of guys that get the large journal 327 engine and push them out to 350 with ease. Do i qualify to attempt this with this block and these heads? I am also reading that I may need hardened valve seats inside of heads for modern unleaded gas? Any thoughts or guidance would be appreciated. thanks