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Really impossible to tell without casting numbers as Chevy was all over the board with these heads. First thought is perhaps a '69-70 350 041 casting - 1.94/1.50 valves and a pretty decent head used in the 330 horsepower factory builds.

Second thought is possibly 186 or 492 casting which could be 1.94/1.50 or (better) 2.02/1.60 valves as found in the LT1/Z28 engines.

Only guesses - get the casting number and we can help you out.