OK, some of the information I provided previously is *incorrect*, so I'm going to TRY to correct/update here.
The facts I’ve learned this week (and seen photos) are here:
1. The ’69 Camaro with JL8 that I've mentioned before is a Daytona yellow, black vinyl top, with black houndstooth interior (76 B / 713 ). It is a 396/350 hp, Automatic. It also had factory installed AC (although not complete under the hood).
2. It’s a 10A car (checking the VIN number it appears to have been produced on 4 Oct 1968).
3. I first saw the car around 1977 when the ‘new owner’ and his friend brought it to my home to show me the car they had just purchased from the local Oldsmobile dealer – off the used lot – it had been traded in on a new Olds. In my ‘walk around’ examination in my driveway, I noticed the 15” Rallye wheels (unusual on a 396 car) so I checked the brake calipers. It had the 4-piston disk brakes, including on the rear axle. At that time, the components appeared 'original' and to have been there since its build, although I didn’t have opportunity to thoroughly check numbers etc. I informed the new 18 yr old buyer that it had a rare disk brake option, and that I would trade the 12 bolt 3.73 posi rear from my original ’69 Z28 for the rear end AND pay him more ‘to boot’ than he had just paid for the car. He didn’t take my offer, although until that point he had not realized it had the 4WD rear. He has since checked all the parts and told me this last week that the car has ALL of the JL8 parts including the rear and front brakes and all worked perfectly. It appeared to me in 1977 to be a factory install – not something converted by someone (and that was in 1977)! He was about to graduate HS, and had told me he planned to go to college in engineering; that fact helped me to locate him years later!
UPDATE from this past week. I called all the numbers I had for him and left a message on his work phone (hoping he still worked there). A few days later he called me back and we talked for awhile. He is admittedly nervous about specific data on him or his car being put on the internet, so his name and vehicle VIN and the photos he’s sent me will not be posted here, but I will post the information from the photos simply to update and clarify the information I previously posted (from my memory and my prior conclusions).
• The car was SOLD to the end user on 18 October 1968 (only two weeks after production), but the ProtectoPlate/Warranty card in the AUTHORIZED SELLING DEALER PLATE IMPRINT area stamped in red block letters is “CHEVROLET ENGINEERING CENTER, 30003 VANDYKE, WARREN MICHIGAN”. The original customer was also identified (Atlanta GA area).
• The original ProtectoPlate for the car identifies the factory installed components (Engine, Trans, Rear, etc). The original engine and trans are still installed, but the differential code shows BM0911G1 (which is for a 3.31 non posi 12 bolt), so the JLK components were apparently NOT installed in the factory as I’d believed on my ’77 viewing. (Question: but were they installed at the Chevy Engineering Center???)
• The rear differential actually installed in the car is stamped QU0129G1. The center section cast date is A218. I conclude that the QU rear was assembled on 29 January 1968 which is ~ a year before the JL8 option was available for order by the public! I became curious if this rear may have been an OTC service duty rear (rather than std JL8), but the owner believes it conforms to the JL8 diff tubes (although in my opinion, available JL8 vs SD OTC rear information is very spotty and not as concise as I would wish).
• The QU rear prefix specifies a 3.07 ratio Posi 12 bot with 4WD (same as what Kurt posted was in his car from factory – based on the ProtectoPlate info. I also wondered, and queried KurtS privately if it was possible that his car and this car were purchased by the same dealer or party in Georgia, and if the complete brake systems may have been swapped between the cars for some reason but KurtS said the numbers didn’t match up. 3.07 JL8 rears have to be very rare and far between I would think!
Conclusion: I was able to get some more specific information about this car this last week and I found out my prior information/assumption was wrong, but it does have ‘factory JL8 components’ installed although we’re unable thus far to determine how/who/when it was installed, but it was well before 1977 based on the condition at that time. It’s strange to me for these two cars (KurtS and this one) to both have JL8 evidences (in 3.07 form) but not match to their POPs… and both being big block cars (which most people have said didn’t get JL8 installed!)… It’s an ‘automotive archaeological mystery’ which I’d love to know the answer to!