http://au.ign.com/wikis/forza-5/Cars
Pretty stoked that the twins are in the game. Apparently every car in the game has been rescanned and rebuilt for the next gen. Interesting that there's no Scion FRS as Forza 4 and Horizon had the FRS instead of the GT86. I wonder if the GT86 will have the Euro headlamps, it's name would suggest that it does.
The Toyota and Subaru lineups are both actually pretty good considering the car list for this game is pretty lean at only 200 cars. But EVERY car is going to be able to be explored in Autovista mode which is pretty amazing. 14 tracks and no Nurburgring til January is sort of a let down, but Bathhurst, Spa and Yas Marina are in so I'll forgive them.
Subaru
1998 Impreza 22B STi 
2004 Impreza WRX STi
2005 Impreza WRX STi
2011 Impreza WRX STi
2013 BRZ
Toyota
1985 Sprinter Trueno GT Apex AE86
1994 Celica GT-Four ST205
1995 MR2 GT
1998 Supra RZ
2003 Celica SS-I
2013 GT86