I don't understand where the PIC12C508 fits in this solution. It seems to me that the sensor could be driven by an Arduino if you wanted, and I'm sure you'll find plenty of examples of people using an Arduino to do that sort of thing since they seem to come up fairly frequently. If you want help using the PIC12C508 the Arduino forum isn't a good place to ask for it, though.
The other point I'd make is, would you really want to use a free-flight ultrasonic device in a safety-critical situation on a moving vehicle at motorway speeds?
I think you missed the point AWOL was making.You are trying to use ultrasonic time of flight from a moving vehicle, do you see a problem with that?
And it will be moving at 60mph.Ever heard of a thing called Doppler?
I must admit, it was more the wind-noise that was concerning me.