I suggest the Sprinter Trueno since it's the most powerful, but you can win a more powerful version of it at the Sunday Cup, so you might wanna wait. Second choice would be the Alto Works since it's light and AWD. Anwyas, here's the info on all cars.
1. Mira TR-XX Avanzato R----------------61 HP
2.Storia X4---------114 HP
3.Demio GL-X--------------95 HP
4.Alto Works Suzuki Sports Limited------------61 HP
5.Vitz Euro Edition-----------------83 HP
6.Sprinter Trueno GT-APEX (Ae86 Type 1)-----------123 HP
7.Vitz RS 1.5----------105 HP
If you want to know their overall rank, power/weight initially, and power/weight possible after all tuning, or engine type/drivetrain let me know, and I'll tell you.