S&W 65-4 here
Chambered in .357. I like the stainless and rubber combo for a truck gun. It's big enough that pulling it may well be enough, and I can reload it more quickly with the four speedloaders that accompany it. I've a dakota 4 dr and am in the boonies constantly. The .357 w/ golden sabers is more than enough for me. All of this, and I've only got around $300 in it; so a theft situation won't ruin my year. And the .38 I routinely carry could feed the 65 if it had to. And my wife loves shooting it too... Win, win, win. I would encourage you to keep others in mind with a vehicle gun--my wife occasionally drives my truck (if I take hers in for service, if she needs to haul some plants, etc.) It's great if you can pick a gun/caliber that anyone who would rightfully be driving your truck would be comfortable using in an emergency. Just my .01 worth...
Edit:...and I'm with TenRing on the 1894C in .357. Just purchased one actually. I just like the .38 spl/.357 mag "group" if you will. Lots of flexibility for all sorts of purposes (hunting, sd, hd, etc.)