Funny. I got a similar story. Back in ought-four, I was bringing my mouse killing machine home from the vet, in my 89 Ranger. The stupid thing had just been neutered and was still kind of doped up. Halfway home I start smelling this REALLY, TERRIBLE, AWFUL STENCH. It smelled like kerosene, like when the torpedo heater in your garage first lights up and doesn't burn all the fuel completely because that cone thing hasn't turned orange yet. That, plus cat piss. It was super-concentrated cat piss because the thing had been unconscious for like a whole day.
Absolutely nothing I did would help. Febreeze, baking soda, coffee grounds, this special stuff from the pet store that's made just for cat urine, etc. Nothing would help.
I had to get to work. The ranger was my only vehicle. I couldn't stand it. It was the middle of the winter and it was miserable driving 30 miles each way every day with the windows down.
I removed the passenger seat and put it in the barn. On days with blue sky, I put it out in the sunlight. 2 years later I was able to put the seat back in the truck.