I'm curious when exactly the key release for manual transmission cars changed. I know the early cars have the tab on the column behind the ignition cylinder, and the later cars have the button on the lock cylinder itself, but I'm unclear on exactly when they changed over.

Also could someone post a nice clear image of the late lock cylinder with the key release? I want to verify that the one I've got is correct.

 

From digging around on my own, it looks like the last year for the old style key release on the column was 1989, and the 1990-up cars have the key release on the lock cylinder.
That would seem to make sense since I was thinking the lock cylinder key release was a 4th gen feature, but I noticed a 91 Z28 I drove a couple years ago had the cylinder key release. The 89 Formula 5spd I test drove years ago had the same old style key release as my 92 S10 and 84 Camaro.

I'm still looking for a pic of a 90-92 key release.

 

No one has a 90-92 5spd and a digital camera? Really?

 

Until someone has a better one to provide, here's an old picture of my 1992 TA 305/5-Speed Convertible. Sorry, mine is currently locked in storage: