I've had 5 rx-7's and one of the 1st gen keys fit my 2nd. Before I became a cop, I worked at the Ford plant and we had a stack of lost/found keys that we loaned to employes to try if they locked their keys in their car. It worked most of the time. I've even used my 2nd gen key to open a 96 Crown Vic. the only thing a key does is keep the honest people honest. Criminals will always find ways to break into our crap and take it. The best way to solve this is a nice loud alarm, but that only works if you or the police are around to hear it. I've seen a guy who put 3 car horns inside the car and connected them to the alarm. He also moved the hood latch to keep them ripping the alarm out. You might end up with a broken window, but your stuff will still be there when you come out.

 

a window is just as exensive...just get one of those sensor so when someone looks in your car a warning will go off.

 

or lo-jack