if ya gotta leave gear in a truck, bolt a heavy duty STEEL box THRU the floor with 9/16" grade 8 bolts and beefy washers, and use Nylock nuts and washers on the other side. Use RED or BLACK loctite on the fasteners to ENSURE they cannot be undone. Use an ABUS DISCUS lock to secure the box.

I did this in my old bronco, and put the batteries, ignition, coil, MSD control unit, plus i had a section for gear. The whole thing was bolted shut and locked. The truck had no top or canopy, or doors. I could leave it in the woods or in the DTES (hells kitchen vancouver) for weeks and nothing would getinto it.