With regards to spark, the better solution is to make a matching wire from the coil to the distributor that has an internal "open" in it. A thief will look at the ignition wires and assume all is ok, but it won't start and it takes too much time for them to debug. With regards to towing, the best you can do is turn your wheel all the way in one direction and lock the steering column. I actually have my lockout linkage removed, and I go under the hood and engage it manually to lock the column. But if a thief wants your car bad enough..
In one of my clubs, they took an entire double axle enclosed car trailer from a well lit hotel parking lot in a nice area. Moral of that story is to never park your trailer where it can be unhitched and reconnected to another vehicle. Wedge it between your truck and a building.