Dave

Nothing simpler.

Yes you can hunt on safari and take whatever you want from the list when booking if the animals are still available on their quota.

Generally there are two ways of booking:

A package hunt. These are very popular in the US and most booking agents push them. Here there WILL be animals that are already paid for and they may include game you are not interested in. The daily rates, trophy fees of listed game and other costs are usually totalled with a small discount. On the other hand if you do not take one of the listed animals you may have paid the trophy fee for nothing. That's how they make the discount pay.
The other way is to book a safari for X days agreeing to pay the daily rates and other agreed costs and then for any game taken or wounded you pay a trophy fee. You should agree with the outfitter what game you are looking for in advance to ensure they are reserved for you on their quota, but some additional animals may be available when you are hunting, but not guaranteed.

Some animals on some game farms or concessions may have additional requirements eg Sable may have a minimum numbers of days required for booking and a higher daily cost. Sometimes bushbuck is the same.

Tell us what sort of antelope are you interested in?

If you want a bargain include an impala. They are very beautiful shoulder mounts with their lyre shaped horns and coat colouring.

As cchunter said some outfitters also offer five day hunts but remember to leave enough days to take the numbers of game you are looking for. Seven days is a good minimum for around seven trophies. A day an animal is a good guide but discuss this with your outfitter.