I realize mothballs stink up the rig, but having enough distributed around will prevent rodents from moving in. Mice can do some serious damage to chassis wiring in the engine compartment, so hang a couple of sacks of mothballs in there too.
Off-season, I store our Saturn Sky
SEEN HERE outside under a make-shift canopy under our deck. Check out the last two pictures. Our property is a rodent city, in part because we feed the birds in the winter. The deck is adjacent to the feeding area making rodents a serious threat to the car. I place trays of mothballs in the trunk and passenger compartment, and hang 3 sacks under the hood. I also plug the exhaust pipe with a tight-fitting plastic bottle to prevent critters from moving in there. It has been working well. Just a little such effort pays back big.
We could use a couple of alley cats. They would have plenty to eat.