I also have a Marlin 62 in 256 WinMag and a Winchester 88 in 308 but, My choice for a truck gun is the Marlin 336 in 30-30.
The 30-30 is a capable round and the 336 is a reliable action. The Marlin 62 and Winchester 88 are hard to find. If my Marlin 336 is stolen, it's no biggie. I have plenty more and they're relatively cheap.
I also have ARs but, if I get stopped by a cop, I think he/she will be a lot calmer with a lever action hunting rifle in back as opposed to an AR. I like for the LEOs to be comfortable. :-)
I carry mine in a saddle scabbard behind the back seat of my F250.
T.S.