I'm probably the only person who's done as much research on the 1987 Camaro convertible (Sport Coupe and Z28). I hate to toot my own horn, but having owned a total of three of these (I currently have one), I know as much about these cars as anyone.
It is the only anniversary GM car that was produced without an official announcement. To that, GM fell far short of expected production numbers, making it the rarest third generation regular production Camaro. An original 1987 convertible will have a map pocket with "20th Anniversary Commemorative Edition" lettering in white, red, dark orange and orange. It will contain a "3" as the sixth digit in the VIN and it will have a unique rear spoiler (with spoiler side extensions on the doors) and a unique center brake light assembly.
The Z28 convertible is extremely rare, followed by the Sport Coupe and the Z28 with IROC-Z option. The Z28 convertible came with only two drivetrains:
1) 305 LG4 / Automatic and
2) 305 TPI / 5-speed.
For reasons unknown to myself, GM did not produce any 1987 Z28 convertibles with a 305 LG4 / 5-speed or 305 TPI / automatics.
I believe this car is definitely a collectible because of its sheer few numbers produced AND it's an anniversary edition. Keep in mind that only the convertible received the anniversary label. Out of a total 1987 Camaro production of 137,760, only 263 Sport Coupes and 744 Z28 convertibles were made (or a total of 1,007 anniversary models only).
If anyone wants to see pics of my 1987 Z28 convertible, please e-mail me.
Supercharged 1987 305 IROC-Z, Daily-Driver, Emissions-Legal.
12.57 @ 111 mph.
12.04 @ 114 mph (50-hp nitrous). http://www.ozemail.com/au/jca69/mods/williesz/willie.html
1987 "20th Anniversary Commemorative Edition" Z28 Convertible -- Super Chevy Show Class Winner, 1998.