Has anyone considered talking to the folks at Vogue Tyres?
https://www.voguetyre.com/
I was surprised to see a white pinstripe (correct for and a great look on some 69 Firebirds), which is available only in one size, 225/60R16. The difficulty would be finding a suitable 16" wheel for the 69 Firebird.
They also offer a redline, in 235/55R17. Might be easier to find a suitable rim for both F and A bodies. Isn't there a Rally II in 17" now, or a modern alloy rim styled like the Rally II? I saw something in Summit TX & GA locations recently but I don't know if they had a 16" or 17" version.