Information was from GameShark Gabe, at http://www.railway.org/gt/gtcars.html, but extensively modified in format.

Manufacturers' Races
East City
ManufacturerRaceNUPDoneComments
Daihatsu Midget - Normal N    
Mira - Normal N    
Mira - Racing N    
Storia - Normal N    
Storia - Racing N    
Honda NSX Trophy - Normal N    
Civic Race - Normal N    
Civic Race - Racing N    
Beat the Beat - Normal N    
Type R Meeting - Normal N P  
Challenge S2000 - Normal N    
Challenge S2000 - Racing N    
Mazda RX-7 - Normal N    
Roadster - Normal N    
Roadster - Racing N    
Demio - Normal N    
Demio - Racing N    
AZ-1 - Normal  U   
Mitsubishi Mirage - Normal N    
Mirage - Racing N    
Evolution - Normal N    
Nissan Silvia & 180SX - Normal N    
Silvia & 180SX - Racing N    
Pulsar - Normal N    
Skyline R34 - Normal N    
March - Normal N    
March - Racing N    
GT-R - Normal N    
GT-R - Racing N    
Subaru Alcyone (SVX) Challenge - Normal  U   
Alcyone (SVX) Challenge - Racing  U   
Impreza Challenge - Normal N    
Suzuki Alto Works Cup - Normal N    
Alto Works Cup - Racing N    
Cappuccino Cup - Normal  U   
Cappuccino Cup - Racing  U   
Tommy Kaira ZZ-S - Normal N    
ZZ-S - Racing N    
Toyota Celica - Normal N    
Celica - Racing N    
Starlet - Normal N    
MR-S - Normal N    
Altezza - Normal N    
Altezza - Racing N    
Vitz - Normal N    
Vitz - Racing N    

"N", "U", and "P" stand for "New", "Used" and "Prize" respectively, and indicate where you can or must find the car. I might get it entirely filled in some time. The important ones are ones where "N" is not available, but you must either find the car used, or win it as a prize.

Note that an additional aggravation is that very often prizes which it seems should be eligible are not. For example, the Mine's R34 Skyline GT-R cannot enter the R34 Race (although it can enter the GT-R Race!?!?!). (And it really cleans up, I might add )