How about a source for "theft proof" screws? My license plate got "jacked" this weekend, spent all morning with Police, Registry and Tax Collector getting everything back Funny, while there, I was able to renew my Drivers License 4 mos early, therein lies the UP side
For anti-theft bolts, try Honda. I worked on Hondas for years and collected lots of them. I have mostly used up my supply.
From 1979 to 1989 Honda used an air compressor by Keihin that had some unique bolts in the cylinder head. They have a slope side with a Torx bit fitting. They are 6mm x 1.0. Without the proper tool the screw cannot be removed. I have had several plates jacked, but none that had those screws in them.
Protection has little to do with alarms or devices. You need to think like the punk. If your junk is harder to pilfer than the junk parked next to it, the punk will pilfer the next car in the line. Like water running downhill, he will take the easy way.
The same works for stereos and driving lights. Be creative. Make yours harder to steal than the other guy's. Then the punk will pilfer the other guy's truck.