That’s a great question; surprised it hasn’t been brought up previously.
Van Nuys produced 31,163 ‘69s, 12.8% of the total. Distribution was initially limited to the western US, primarily CA, AZ, NV, WA, OR. The rest of the US received cars built at Norwood. Van Nuys stopped building ‘69s at the end of June 1969. Norwood continued producing ‘69s through mid-July 1969 when it shut down for the annual model changeover. Only, there wasn’t one. The 1970 Camaro tooling was not ready, so Norwood resumed producing ‘69s as of August 11. Van Nuys did not. Dealers that had received Camaros from the Van Nuys plant were now supplied by Norwood.
The Van Nuys plant was on strike April 28 - June 1. Some VN orders may have been diverted to NOR. The survivor L78 SS seen at MCACN a few years ago was built at NOR April 30 and shipped 1,800 miles to Tucson, AZ.
While many people have deep experience with ‘69s, it is most often limited to one plant; few people seem to have experience with cars from both. It has taken a long time to note the differences that are known. Here’s a few others:
Some VN Z/28s have the rear striping in the vinyl top configuration even on cars w/o vinyl tops. A few very early VN Z/28s have the 1968 rear stripe layout. VN was much neater painting the stripe color on top of the cowl; early NOR cars can be very sloppy. Also, appears VN was more precise in masking the wiper panel for stripes.
NOR typically sprayed sound deadener in a squared-off pattern on the inside of the rear quarter panels behind the outer wheelhouse. Have not seen that on VN builds.
Cars built with dual exhaust at Van Nuys have been found with the tail pipes painted black.
The foam pads at the top of the cowl are glued to the wiper panel on NOR builds, glued to the body at VN.
VN used the same body tag blank for the entire production run. NOR switched to the larger tag mid-November 1968.
On NOR builds through the end of October '68 with green, red or blue interiors, the VIN tag paint matched the top of the dash. Starting November '68, they were black suede for all colors. Fairly certain VN VIN tags were always black.
I’m sure there were other differences.