The P&A 34 ("Chevrolet parts and Accessories Catalog for 1960-1969 Corvair, 1962-1969 Chevy II, 1964-1969 Chevelle and 1967-1969 Camaro") was a "dealer only" book showing the parts numbers for all the items on your car. It was accompanied by another book called the P&A 25 ("Chevrolet Passenger Parts Illustration and Special Information Catalog") that was a book of exploded parts diagrams. Together, these two books are what the parts counterman (or woman...) at the dealership used to look up and order replacement parts for your car. My particular P&A 34 and P&A 25 are from September, 1968 that I've had for some 30 odd years!
Finding these things is just happenchance. I've seen them on ebay VERY sporatically (one or two in twice as many years), but some of the larger automotive book dealers sometimes have them. Here are a few you can check with:
Faxon Auto Literature (800-458-2734)
Chewning's Auto Literature in Georgia (sorry, no number)
Bob Johnson's Auto Literature (800-334-0688)
Douglas Vogel Auto Literature (734-424-9336)
Paper Plus Auto Literature (616-781-9068)
Walter Miller (800-426-0902)
Paul Politis Auto Literature Shop (800-526-7099)
Now, these phone numbers are fairly old and seeing how area codes change every few hours lately, you may have to do some detective work! And I'm not sure just how many of these guys are still in business, but give it a shot. Won't hurt to try, but be prepared, the one's I did see on ebay went for HUGE
$$$$!!! Especially the sets like I have. The last ones I saw was a matched set from 1970 and they went for over $700.00! And this was a few years ago. I can just imagine what they're going for now!!!
Edit: A quick check of ebay shows a P&A 34 from October, 1967
. No P&A 25 though.