i personaly think anything rwd would be fun for both auto-x and rally-x, which leads me to propose the mid-80's Toyotas (corolla?) with rear wheel drive (the hachi-roku or how ever you say it) or maybe around the same time a nissan 240sx. both can be had for cheap, can be reliable if maintained well, parts arent to hard to come by, and rwd is fun for sliding around in the dirt and gettin' sideways on pavement.
cheap awd cars are harder to find, and just have more driveline parts that can break. fwd cars can be fun, you just have to use the e-brake rather than the throttle to get sideways.
mark