I'd hunt the pawn shops for a a low powered Leupold, and stick it on a Marlin 336 3030.
I am with Dee in looking for a used Leupold VarX II 4X 24 , or a Weaver K4 4X38.
I think a new K4 is under $180 if you pay Tax, and express shipping. I think the Weaver K and V lines are = to the leupold Var X II line in quality and light gathering I own both but have been putting Weavers on the later rifles.
I have a Leupold 4X on a 375H&H and a Weaver on a 22Mag the Weaver seems clearer and gathers more light at dusk.
I am a bolt gun fan so a K4 on a Sporterized Mauser 98, 96, 93, 95, or even an Enfield No4. That can be picked up cheap. Any of the WWI military rounds will work for a truck gun.
I actually think a Enfield No4 would be a perfect truck gun if you do not want a scope. The large peep sight is great for fast shots and a flip of your thumb and you are at the small peep that you can pre- set to yardage.
The 303 Brit with 150 or 180 grain soft bullets is 30-30 plus 150 FPS. The detachable mag makes mounting a scope easy as you so not have to leave room to load rounds and a loaded mag can be carried and just snaped in if you can not have a loaded rifle in the truck in your state. Same it can be unloaded fast. By opening the bolt and then removing the mag and topping off the mag with the round from the chamber.