We borrow an Ifor Williams from the farmer, not sure which model it is, but it is high enough for us to stand in, it has barriers in the middle and at the ramp's end, and a split door at the other end towards the car (necessity!). All metal, but wooden panels to go in front of the open 'windows' at the top.
Our 5 large pigs had enough space to stretch out whilst sleeping in there overnight.
Get the biggest one your car and bank account can cope with -the pigs will be more relaxed if they're not in a claustrophobia-inducing little space, and it'll be easier for you, too.
Eve