I'm driving the 400R.
This is the Normal Series. There are only 6 AI cars which ever show up:
NSX TypeSzero
TRD 3000GT
Impreza'96WRX STi VerIII
efini RX-7 Aspec
R33 Skyline GT-R
Lancer Evo IV GSR
So an AI field can be characterized by which of those six is not present. (GT1 always maximizes the number of manufacturers represented in the AI; so you always get 5 different cars here; in e.g. the Lightweight series or USvsUK there are only four manufacturers it chooses from, so you actually get duplicate cars (not only manufacturers, but cars; when there are only 5 or fewer manufacturers, with some manufacturers having only one choice, their car always shows up, e.g. Impreza in USvsJP or RX7 and Lancer in Tuned Series; for some reason when a manufacturer needs to be duplicated, you can actually get two identical models of car, even if the manufacturer has other choices )) But, in any case, the AI never drives a 400R in the Normal Series.