I definitely second Randy’s concern about chasing in an older vehicle. I am a chase vacationer and always rent, but even with the relatively new cars you find at rental places, I am always paranoid that something is going to happen. In fact, one reason I prefer flying into large airports like Denver is for the large selection of rental cars. I have been given vehicles with bald tires, or with the “change oil” light on, so it’s good when there are enough vehicles available to get a proper replacement.
The point is, the reliability of your vehicle, driving the vast distances of the Plains, where you are often out in the middle of nowhere, possibly late at night, is analogous to having a seaworthy vessel in the middle of the ocean.
I also second Randy’s advice about tires… The problems I have had with rental cars mostly involved flat tires. Sure, roll over a nail on a dirt road and you’ll probably puncture even a brand new tire, but you need to stack the odds in your favor, and control what you can control, to give yourself the best likelihood of traveling without incident.
One of the worst things I could imagine is a vehicle that won’t start or move when you most need it to escape!