Body numbers are issued by series, and in 1967 there were four series of numbers issued for Firebirds. Standard interior coupe, standard convertible, deluxe/custom coupe, deluxe/custom convertible. Yours as a 22467 has the standard interior, and was the 31st (looks like 81 to me in the photo) of its series scheduled for production.



I don't see anything that references 5,641.



A.I.R. was emissions control, air injection reaction. This consisted of an air pump and pipes with fittings threaded into tapped holes in the exhaust manifolds. This is a '67 California emissions equipped car.



The number on the front of the block is called the Engine Unit Number and is found on the Pontiac Billing History for most cars through 1968. Although the series did start with 2, the numbers had already reached over 100,000 more by the time your engine was built, so the first number was a 3. YJ is the code for a 1967 Firebird 326 2 bbl engine with automatic transmission. http://thefirstgensite.com/library/engines/enginecodes.htm



The 140 head casting is the correct casting number for your car. You will need to verify that the casting dates on all your components are before mid January 1967.

That "other" number is 18436572, it's cast on the intake manifold, and it's the engine's firing order.