The only real clue would be the codes on the build sheet, specifically, boxes 5,6,14,37, and 39. Down on the bottom left hand side of the build sheet is the COPO code. If the car is original it will have the specific engine code as will the rearend. The fenders and rear filler panel won't be pierced either. Everything else was pretty well standard parts used on other Chevelles. Chevy kept it all pretty simple. I never found a build sheet in either of our Baltimore cars. Happy New Year.
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Chevelleless after 46 years......but we did find a low mileage, six speed, silver 2005 Corvette. It will just have to do for now.