[John V.]

Eric, I can say that Fremont was Code F in '64 with confidence based on my own '64 GTO built at Fremont, Plant Code F in the VIN.

Pontiac started all Plant VINs from 1001 in '64. Leading 0s were added to form a 6 digit VIN sequence no. on the paperwork (leading 0s were not embossed on the VIN tag itself), so 1001 is also 001001. At Fremont they ran up to about F040000.

Olds also used the virtually identical VIN format as Pontiac in '64. Since the Cutlass series was also built at Fremont, the way they were assured of keeping them from having two cars with identical VINs, Olds started their VIN sequence no. at 100001.

So it was possible to have a Lemans with VIN 824F012345 as well as a Cutlass with VIN 824F102345. Very, very similar but never identical.

Same was the case for the Kansas City, Missouri Plant that built the Tempest series alongside the Chevelles. Since the Plant Code was M, you had the possibility of identical VINs with Cutlasses built at Lansing.

This was avoided again by the fact Pontiac VINs started from M001001 and ran to about M030000 while Lansing VINs started from M100001.

Can't say how confusing this was for GM to have 2 Plants with the same Plant Code. But keep in mind that at this time, the Final Assembly Plants were under the autonomous control of either Chevrolet Div. or the B-O-P Div. In other words, the Car Divisions controlled the Final Plants and Chevrolet could have a Plant Code A and the B-O-P Div. could have a Plant Code A (and both did).

When GMAD was created in '65, Chevrolet & B-O-P final Plants were united under this one umbrella and that is why the new Plant codes had to be assigned to eliminate the duplication. Prior to that, it does not seem to have mattered since there were plenty of duplicated Plant Codes between the two Car Assembly Divs (Chevy & B-O-P). From what I can tell, Cadillac may have remained outside of GMAD at that time and continued to autonomously control their own final assembly Plant(s).

All the while, Fisher Body remained an independent GM Div. Fisher Body workers were organized under different union locals from the guys in the Final Plants. The formation of GMAD only affected the Final Plant organization at first, Fisher Body continued under Fisher Body management.

That did not change until GM Corp. made the announcement in '68. The rationale was to streamline production. Up til then, both Fisher & the Final Plants operated their own Paint Shops for example, Fisher painted the Body Assembly, the Final Plant painted the front end sheetmetal. I suspect that having to negotiate contracts with two separate union locals was also considered a nuisance since a strike by one would idle the entire operation.

Can't offer an explanation for the changing Data Plate formats but the '65 creation of GMAD out of the Chevy and B-O-P assembly operations did not affect the Fisher Body Div. at all from what I have seen.

Clark St. was the Cadillac Final Assembly Plant from what I can tell from the time it was built in 1921 until the Hamtramck Plant was built in the '80s. I believe all Cadillacs were assembled at this Plant until '71.

Fisher Body did not have a Body Assembly Plant at the Clark St. complex. Instead, I believe Cadillac bodies were assembled at what I think was known as the Fisher Body Fleetwood Plant, some distance away from the Clark St. Plant in Detroit. Located in Delray at the corner of Fort & West End according to references I've found. Also called Fisher Body Plant #18. The completed bodies were moved by truck across town.

It was known as the "Fleetwood" Plant because Fisher Body had decades before acquired the competing Fleetwood Body operation and eventually moved it to this Detroit location. However, despite the fact that Cadillac had a Fleetwood model, the Body Plant cranked out all Cadillac models. There were probably exceptions. As for example, the Eldo bodies that you show being produced at Euclid.

Now, looking back at your Chart, the Clark St. Plant seems to be one and the same as what you show as the Mack Ave. Plant.

From a Cadillac VIN decoder, Cadillac began putting a Plant Code in their VIN in '71 (presumably it was not necessary prior to that).

If I read it right, starting in '71, Sedan DeVille Hardtop and Coupe DeVille production was shifted to Linden (Plant Code E). All others remained at Clark St. and were coded for Plant Code Q.

I looked all around. The Clark St. Plant was located at 2860 Clark St. and known at that address until it was closed and demolished by everything I can find.

I cannot find any reference to a Cadillac or GM Assembly Plant on Mack Ave. I don't know Detroit, but it does not look like Clark St. crosses Mack Ave. today, although possibly before new highway construction, maybe it did. But what I do find, suggests that Mack Ave. turned into Myrtle Ave. as it went west and Myrtle later was renamed MLK Blvd. west of the John C. Lodge Freeway at some point. This road runs out to about West Grand Blvd. where it ends. Meanwhile, Clark St. currently appears to terminate just east of Michigan Ave. (US 12) and just to the southwest of where MLK hits W. Grand. If Mack Ave. ever ran all the way out to Clark St., I can't find evidence of it. And nowhere do I see any reference to the Clark St. Plant being referred to as the Mack Ave. Plant.

Yet, everything else about the dates and such that you show as Mack Ave. matches to info about Clark St., including the identification of the associated but separately located Fisher Body Plant as Code FW, undoubtedly to mean Fleetwood and located at Fort & West End, a few miles to the SW of the Clark St. Plant and just off what is now I-75 (Fisher Freeway).

Curious how you found it to be named Mack Ave. I think it should be identified as Clark St.

Hope this helps.