Through experience I've found these crates to be the best, really robust construction and cheaper than Savic or similar. A GSP will need a 42" or 48", I reckon. I use vetbed in crates, it washes and dries quickly, wicks away moisture and is cheap, you can buy strips on eBay. When older and accident-free they get a nicer squashy bed in there.
In the crate in the boot for preference, I've got a bit of a thing about dogs being unrestrained in cars, in the event of an accident they'll be straight through the windscreen. A crate for a pup or a proper dog guard and tailgate for an adult is a must.
Essential reading: Don't Shoot The Dog, The Culture Clash, In Defence of Dogs and anything by Ian Billinghurst on raw feeding.
You will need a plain collar and lead, ID tag (these ones are good, deep-engraved, last ages), food and water bowls, poo bags, a couple of chew toys, probably a kong with which to stuff with food to aid in crate training if not raw bones from the butcher, endless patience and a good sense of humour. 