I've had a puppy for a few months now...a failed foster. He spent the first few months of his life in a crate with no socialization. His first ever car ride was when some stranger grabbed him, wrestle...
You could try introducing car travel slowly. A trip around the block, a short drive to the park, etc. Find his comfort zone, then slowly increase the length of time. Dogs often adjust to travel as they get more comfortable. A thunder shirt might also help.