Well, there are a lot of misconceptions about the 30-30. People saying its weak or a 100 yard round. That's simply not true. And now with Hornady's Leverevolution, you can comfortably reach out to 200 yards minute of deer with 160 gr bullet. So, I would not discount the consummate lever gun round. For a truck gun for a lefty, a Rossi R92 (Winchester 92 clone) in 30-30 would be hard to beat. While it still ejects to the right, the 92 is a top eject and will chuck empties up across his forehead rather than across his line of sight.
If you want more distance, a Savage 99 that will handle a spitzer bullet is a great idea. But I wouldn't be slinging mine in the back of a truck...