I moved from the East Coast to the SouthWest almost 3 years ago. We had to find new homes for 8 of our cats (yes, we had 10 in the house. Never again!) and it was very difficult. I thought that my 12-13 year old very skittish and mostly antisocial cat would be terrified on the car trip and would have a difficult time adjusting. I tried to find a new home for him, but no one wants a 12 year old cat - it's just too "old", and they do not want to deal with age-related vet bills. As it was, when I adopted him from the shelter in 98, he was 3 and had been there for almost 6 months.
I took him with me. Just me and him, on the wide open highway. [We'd moved the other two a couple months earlier.] He'd be noisy when I put him in the kennel, but he'd calm down and ride out the trip with me. Finding him the next morning was always fun - it's amazing how a B&W cat can blend into things. I tried to put a harness on him before we started the trip - so he'd be easier to grab, but he was having None Of That and laid into my hand. We played "catch me" while on the road in the motel room, but once caught, he wouldn't wriggle and scratch, just meekly get into the kennel.
He adapted to the new place just fine. There was some cat-hierarchy issues, but they sorted themselves out. He ruled the upstairs and the other two ruled the downstairs.
He was a perfectly healthy 13 year old cat when we moved and he was happy with his new environs. I think if I'd found some place else for him to live he'd be really unhappy with new people. He only really tolerated me, and even after 10 years with DH he would -sometimes- allow DH to give him an ear scritch, but ONLY if DH was sitting on the toilet. DH was not allowed to approach him.
Just my experience. Like I said, I originally thought he wouldn't weather the move and transport well, but he surprised me and it turned out to be the better decision.
It is just really hard to find a new home for an old cat. Primarily because of possible vet expenses. [Patches cost us almost $1 last year, which would have been more if we really wanted to find out the extent of his brain tumor.] But they also do not want to feel responsible if nature claims your cat.
Look into Kitty-Valium if you take him. I knew Patches would be mostly OK since it was us on the road. But if I had to fly with him he'd have been freaking out for all 9 hours.