I started playing this again this week
Then I finished season 10 so I decided to have a play at building a high powered American classic (never really used them before). I started off with a standard Dodge Dart Hemi Super Stock (C424) which ended up with 927HP, Twin Turbo's, V10 Viper engine and a lot of other bits. Surprisingly it stayed at C424, 0-60 in 2.351, 0-100 in 5.552 but unfortunately the standard gearbox means it can only do 111mph (upgrading it made it R3 I think).
It still won a classic Dodge race around Catalunya fairly easily though