Information gathered from various sources over the Net. I haven't confirmed much of them myself.
When there are two cars to choose from, it is SUPPOSED to be chosen randomly, but apparently it's not very good randomness. But after you watch the ending (staff-credit) movie --- either from Quick Arcade Goodies menu, or by winning GT World Cup --- the randomness improves, until you reset or turn off the power.
You don't need to win endurance races to obtain bonus, just complete the race.
| With condition | Bonus Car | Other info |
|---|---|---|
| Sunday Cup | Mazda DEMIO A-spec | Silver |
| Clubman Cup | Camaro Z28 30th Anniversary | White+Red |
| Gran Turismo Cup | Toyota Chaser LM Edition | Black |
| Gran Turismo World Cup | none | (GT HiFi becomes available in Special Event menu) |
| FF Challenge | CR-X EF-8 SiR | Purple, Yellow, Black |
| Celica SS-II | Purple, Yellow, Green | |
| FR Challenge | Sil Eighty | Blue, Yellow |
| Silvia Q's 1800cc | Purple, Blue, Yellow | |
| 4WD Challenge | Lancer GSR Evolution IV | Green, Yellow, Purple |
| Alcione SVX S4 | Purple, White | |
| Light-weight Challenge | Civic type R | Black+Yellow, Black+Pink, Black+Lightblue |
| Eunos Roadster | Yellow, Gold, Purple | |
| Japanese vs American | Mitsubishi FTO LM (4WD model) | Black, Green |
| Dodge Viper GTS-R | White+Green, White+Blue | |
| Japanese vs British | Honda CR-X Del Sol LM (MR model) | Red, Black+White |
| TVR Cerbera LM Edition | ||
| British vs American | RX-7 A-spec LM Edition | Blue, Green |
| Chrysler Concept Car (Racing-modded) | Yellow, Purple | |
| Mega Speed Championship | Soarer 2.5GT-T VVT-i | Yellow, Red |
| Aston Martin DB7 Coupe | Purple, White, Dark red | |
| Normal-Car Championship | Impreza '96 Sedan WRX STi ver.III | Orange |
| Supra RZ | Orange, Lightblue | |
| Tuned-Car Championship | AE86 Sprinter Trueno GT APEX | Red, Blue, Green |
| R32 Skyline GT-R '91 | Yellow, Red, Blue | |
| Grand Valley 300km Endurance | Castrol Supra GT | Black+Red+Blue, Black+Red+Green |
| S.S. R11 Endurance | S14 Silvia LM Edition | Green, Red |
| S.S. R11 Endurance II | NISMO GT-R LM Edition (Stock, FR model) | White |
| All Gold in B License Test | Chrysler Concept Car | Red |
| All Gold in A License Test | TRD 3000GT | Silver |
| All Gold in International A License Test | NISMO 400R | Gun Metallic, Yellow, Red, Silver |