Hutch, back when I had a series of CJ-5s (damn, I miss those .... the last of the real Jeeps!) I used a Bestop storage box and never once had a break in, even though all my Jeeps were rag tops. It may be plastic, but it's pretty tough stuff, i.e., it'd take a thief awhile to cut through it. If you're concerned about the lock, you can drill that out and install a standard hasp and padlock arrangement with little trouble. That's what I eventually did.