I worked for a few years on body controllers, usually 4, 8 or 16 MHz/16bit. On the cluster side, I saw for example 28MHz/16 bit (Smart electric with 206x64 dot matrix display). I know from my colleagues in the power train department that they currently use 180MHz/32bit controllers (with cryptographic flash code signatures and stuff).
Now I am back to body controllers and it seems that here the industry is moving to 32 bit PowerPC architectures (it even has error detection&correction capabilities). On body controllers, even if the controller can run at 64 or 80 MHz, the controller is clocked at much lower speed (4 ... 8 MHz) for the sake of current consumption.