I am surprised that this wasn't mentioned:
(going off memory here) When Rocky Rotella set out to create a 'Definitive' 1967-1981 Firebird & Trans Am book, it quickly became apparent that it needed to be released as a two book set;
The first book was released as a nice hardcover book, and had an entire chapter dedicated to the 1969 Trans Am - the book is a very good read.
It looks like it's currently sold out - but odds are you can find it on Abebooks.com (a web resource for book sellers) or eBay;
I highly recommend this book.
Here is Rocky's own site showing the book:
LINK
EDIT: CRAP-SANDWICH - has this one shot up from greedy resellers!! (
AbeBooks link)
Don't get me wrong, if someone can sell a $54 book for $600 - power to him, but this is really unexpected - I have been seeing since covid & book sellers slimming their available books that resellers have gotten exponentially greedy.
(because our host downsizes attachments, there are currently six available;
The "cheap" one is $253usd + $60usd-shipping(!!);
The most expensive one is $599usd + $38usd-shipping.
(attached is a modified screen shot showing hte top and bottom two - organised cheapest total on the top.)