>>28568091
Z28 was the secret track trim in 67/68 before it was properly advertised for 69. At the time bigger number meant better but the DZ302 being smaller than the 350 or 396 or hell even the base 327 V8 at a time when they were primarily used for drag racing meant that most people opted for the larger engine. It wasn't until 69 that people learned the true potential and purpose of the Z28 wasn't at the drag strip but around the track. GM management killed the DZ302 because they felt it threatened the big blocks. It just happened to be that SCCA changed the rules around the same time allowing for larger engines meaning that in 1970 Z28 came with a 350 LT-1.
And then a perfect storm happened with the oil crisis, the EPA and insurance agencies killing all the fun. The Z28 badge had become as popular as the SS in the early 2nd gen but now with SS gone only Z28 was left now as a package instead of a trim. Being that it originally was a track and handling focus trim in the first gen it was a good fit for the now emissions-choked models with improved suspension but the regular engines. And then it went away for 75-76 because GM-moment only to come back because Pontiac kept the Trans-Am name.
For the 3rd gen, because SS was kill, Z28/IROC-Z were the top trim.
For the 4th gen, because SS was still kill until 96, Z28 was the top trim. There were a few years where it was a Z28 SS. There was also the semi-official 2002 ZL1.
ZL1 goes back to the 1969 models with the detuned 427 L88. Only 69 were built and most were destroyed after that racing season.
5th gen ZL1 made more power but was designed for drag racing while the Z28 made better use of its power around a track. There was a rumor of Z28 coming back for the final years of the 6th gen using the LT6 from the C8 but that was quickly killed as the time and money needed to make it fit wouldn't be worth it at the price point or sales volume.
