You will most likely unlock this achievement on the very first car to choose at the start of the game, as only starter vehicles can be transformed into any of the 5 specs, unlock most other cars in the game. There is no particularly superior car that you can choose from at the start, so any choice is satisfactory. You will unlock new specs and their events as you level up. Spec unlocks are show below;
-Sports – level 1
-Dirt – level 10
-Perf – level 20
-Raid – level 30
-Circuit – level 40