Anytime you start combining option %'s, you're making guesses. And I think you're going the wrong way - I'd say more than 6% convertibles since it's a lower hp engine.
I don't understand why you mean by a lower hp engine. You have the base 6, 6 Sprint, 350, 350HO, 400, 400 HO and RAIV. I am making guesses because I don't have the data, but the logic assumes convertibles would be less likely to be ordered with a higher HP engine.
The total of 112 69 Firebirds with the 350HO is floating around the web and it originated from West Peterson (Editor of Antique Automobile), but the link is now dead.
69 Firebird 350HO Palladium silver convertible 4-speed and 69 Firebird Champagne with a green convertible top 350HO automatic.
