John V wrote the best summation: Lordstown stopped building '69 Firebirds late in March, the latest Time Built codes are 03-B and 03-C.
In mid March, Pontiac "decontented" the Firebird to reduce the base price. One of the things eliminated from the base content were the Drip Moldings. At that point, you had to order the Decor Group option to get them.
At the same time, Lordstown began coding the 03-B and 03-C Data Plates. The most common code seen has been B80. A couple of odd codes have also been reported which may have been coding errors, misreads, etc.
The codes have been found on coupes and convertibles. Drip moldings are nonsensical on a convertible. Since convertibles wouldn't have Drip Moldings, a B80 code on a convertible either indicates a coding error or else the code refers to the Decor Group option.
I have yet to see a code on an 03-B or 03-C Lordstown Data Plate for a Firebird that was documented as not having the Decor Group option.