In 99% of the cases you will not find a build sheet in a Nova - until around '72. However, you will find a body broadcast sheet, and because this car is a '69 Nova (as opposed to a '70) you are in luck. The Nova broadcast sheets for '68 & '69 had the engine designation on them, ie; L34 vs. L78, this practice stopped sometime during the '70 model year.
You should be able to find one of these sheets in the seats, up to 4 have been found in the same car. They are generally on the passenger side of the front & back seats, one in each cushion - ie; seat bottom and seat back. Usually, the most preserved sheet is in the back seat, back portion, and is commonly inside the hog rings that hold the seat cover on. The mice will usually get ahold of these sheets, and partial amounts are chewed up. If you see a mouse nest, don't throw it away, I've been able to pull sizeable pieces of the sheet from their pile.
Finally, don't be surprised if you find a sheet, and it does not pertain to that particular car. The first step is to verify that the body sequence number on the sheet matches the body number on the trim tag. It is very common to find the correct seats in the car, but simply not the exact set that was supposed to be installed. In a case like this, the only code that usually matches is the interior.
Best of luck
