Huh? Only one #13 casting. Used in '70 on HO/RA 400s with auto trans mostly. Not on 350s. No big-valve heads were used on 350s 'til '75.
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'72 Formula 400 Lucerne Blue, Blue Deluxe interior - My first car!
'73 Firebird 350/4-speed Black on Black, mix & match.
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