Maybe? Sr3 was definetley planned to have, junkyard, dealerships, speed shops, catalogs and the newspaper. i maybe missing a few more. One that was never defintley was weather you'd be able to explore the city due the large amount work needed and huge lack of information of the cities at that time period as it was planned to be as historically correct as possible. So i always assumed this one was a maybe.
I really like the idea of Scratching for Parts in the JUNKYARD. The Thrill of finding Unique parts or great deals would be awesome!!! THUS my suggestion is......
In the NEWSPAPER, under parts you can say... MUSTANG FASTBACK
breaking for spares. In real life the car would probably have severe accident body damage, but many components still be 100% functional or damage. You would not be able to buy the complete wreck as the breakers make more money selling it piece by piece and each week there could be less and less of the car renaming. and these breakers are not really concerned about performance parts they are not ENTHUSIASTS there are they to make money so they will sell you a GM 5 Speed racing box for the price of a GM 4 speed box. The WRECK could have been stock or it could be highly modified, by you VIEWING the car you can identify if its a performance part or not, you could look at what parts left and make offers and when you get back to the workshop you can see the parts true identity and the condition (60% Worn) etc...
Is this still going to be a option to send a item to be reconditioned?
If the game is set in 1970 you could get a NEW 1970 Mustang gearbox, how ever for lets say a 1932 Ford T Bucket you would not be able to get a NEW Gearbox, only a second hand or Reconditioned UNIT.
Surely NEW cars or cars that are upto 5 years old can be purchased threw the Dealership. Were the older will be found in the Newspaper and you would interact directly with the owner(can also negatate priced with them)
SPEEDSHOPS will probably only sell NEW items and maybe there can be a old timer advising you on performance upgrades and trying to sell you more items....