I have a copy of the PHS document for your friend's car.
It is a fairly early Pontiac Plant build.
The codes in the Production Instructions box on all '64 Pontiac Plant manifests are the Springs and Shocks codes for the build. Early year cars used a different format for the codes than late year.
I don't pretend to know what the "dealer" code 99 998 represented, but I am certain it was not exclusively the domain of any entity called "Pontiac Motors Racing Division", if in fact that was ever an actual entity within PMD. Since that decode is not attributed to a specific invoice or manifest record, I am at curious as to what information led to that conclusion.
In any event, there does not appear to be any "racing" heritage associated with the subject build.
All '64 GTOs got the same Springs, there was no heavy duty option for GTO Springs. The only "exception" was when the car was equipped with A/C as this convertible was (Sales Code 581) in which case specific Front Springs were specified and differed depending on whether the car was equipped with manual trans or auto trans.
Since this car was equipped with auto trans, it got the "M" code Front Spring set, "LA" code Rear Spring set. Early year GTOs without A/C got Spring Codes "T LA".
Shocks were code "GP GP" unless the car was equipped with the "Rally Handling Kit" option Sales Code 612 or the "Heavy Duty Springs & Shocks" option Sales Code 621, in either of these cases the early GTO codes were "GG GG" for the Heavy Duty Tempest Shocks.
I'm not positive, but I think that somehow the early codes may have been related to color codes or paint daubs associated with the specific parts.
TAG LA CO CAR P HARRIS would indicate the car was destined to be a Company Car for somebody named "P. Harris".
The code 99 998 would have been the location where the car was destined to be delivered and by my guesstimation, the "99" would have identified the Dept. or GM Div. that would have been internally billed for the asset, in other words, billed for accounting purposes.
The build reflected an "add/delete", the car was built without Sales Code 512 so that a credit was issued to reduce the original invoice amount.
Later the car was sold, as Company Cars always were and another "add/delete" accounting entry was made for "Undercoat" at $20.00 and I believe "Fla. Lic" at $7.00.
I'm not certain it reads "Fla", however, the Zone Sundry Invoice No. "17-2596" I believe is to indicate Zone 17 which was the Jacksonville, Fla Zone covering all of Fla. This Debit entry was to bill (again for accounting) incidental added costs associated with the car that were incurred while it was in service as a Company Car.
The "Undercoat" suggests to me that the car was delivered to the Jacksonville Zone by way of a Dealer who added a $20 charge for undercoating, this was pretty typical for a lot of Dealers to add as part of a Dealer prep package (and the "pure profit" kinda game playing that has always gone on in the biz
) and/or may have been something that particular company exec who had use of the car asked the Dealer to do prior to delivery.
Ordinarily, I would have expected the record to have shown 17 99* if it originally went to a company employee operating out of the Jacksonville Zone.
In this case, maybe the guy was attached to some other Dept or GM Div. ("99") but working in Fla.
The "TAG LA ..." could be a typo, perhaps should have read "TAG FLA ..." or perhaps "LA" is a clue to whatever Dept. or Div. "P. HARRIS" worked for.
Could be some other "special" reason for the 99 998. But this was no race car. It was heavily optioned which is very typical of Company Car builds and all indications are that it was placed into service initially as a Company Car and likely originally registered in Fla by a GM employee as such.