The IRS is going to want roughly 35% - 40% of whatever you get. Been there, done that. If the car is valued at $250,000 then you'll have to pay $87,500 in taxes (at 35%). If you take the $100,000 cash, you'll pay $35,000 in taxes (again, at 35%). Plus, if you take the cash you'll actually have the money to pay the tax which you probably won't have if you take the car (at least I woudn't). Also remember that this will be added to your current salary as income for the current year. Unless you are currently making $250,000/year or more this is going to put a serious hurt on you tax wise.
You may be able to tweak these numbers a bit, depending on your personal circumstances and the creativity of your accountant, but the bottom line is that unless you have $80,000 or more in available cash to pay the taxes you're probably better off to take the cash instead of the car. I'm not a tax expert, so it may be possible to take the car and sell it quickly enough to make it worth your while, but my guess is that's a gamble.