Speaking of casting #'s........I bought a 68 camaro (rusted out front cap) that had 210,000 original miles on it. The guy kept a book in his glove box every time he did anything, tires, oil, greased, brakes the works.....The first entery in the book was were he bought it in 1972 with 26,000 mile and was missing. Next entery was Replaced broken rocker arm at chevy dealership. Everything else was regular stuff until it jumped time at 210K. When I was checking the 327 2bbl numbers the heads show as a 1968 307 head. Did they make the 307 then? Did the factory put the wrong head on? or maybe a sneaky mechanic did a switch of the heads instead of fixing the rocker. Any ideas...