[JoeC]

Here is my estimation "Theory" (not fact) on why I think the figure 323 COPO Chevelles built is too high and is more like 200 total of which 99 were Yenkos.

Some people use the number total of 1338 COPO Camaros and COPO Chevelles built (derived from the number of engines produced) to estimate the number of cars built. The engines were built on a forecast of car production and I believe it is too easy to over estimate car production using engine production since it can be up to 100% inaccurate. There were situations where engines were assembled and stamped with a code for a car that was never built. If you use engine production to estimate that particular cars production number you would be 100% off. Another example is the 1969 ZL1 Corvette where over 80 engines were built and stamped and 2 cars were sold to the public.
According to a Chevy service documentation in ED's book there were 700 427 COPO cars "in process" on July 7, 1969 including ZL1's, Yenkos, COPO Camaros and COPO Chevelles. It is not clear what they mean by "in process" but I would think the trim tag date on a car that was "in process" in July would have the trim tag date July or later date. If you take the 700 COPO's and subtract the known cars - 69 ZL1's, 198 Yenko Camaros, and 99 Yenko Chevelles you get 700-69-198-99=334 remaining COPO cars that were non Yenko non ZL1 Camaros and Chevelles built as of July '69. If you take the engine numbers estimate and subtract Yenkos you get 1338-198-99=1041. That would be 1041 engines left to be put in 334 non Yenko non ZL1 COPOs after July '69. 1041 is a big difference compared to 334 non Yenko non ZL1 COPO cars refered to in the service letter. (The ZL1's were not included in the 1338 engines total so I didn't subtract them)
If the Chevy service document is correct, and there were 700 COPO cars "in process" on July 7, 1969 then they would have to have built 707 more COPO Camaros and Chevelles between July and Nov 1969 (1041-334=707) to match the engine production total. No way they built 707 non Yenko non ZL1 COPO cars with July or later build date. I know the 1969 Camaros ran late into Nov.'69 but I have not heard of that many COPO cars with a trim tag date of July or later so I find it difficult to believe they could have made 707 COPO cars after July'69. The trouble with this theory is I don't know how accurate the Chevy service letter is that stated 700 units were "in Process" on July 7, 1969.
This theory combined with the fact that not many COPO Chevelles have surfaced, and there were problems with selling them later in the year, leads me to believe the 323 number is on the high side. I would guess its more like 200.