See the following Q and A from Agha Sistani:

Question: Is it permissible for a Muslim to sell pork to those who believe it is permissible for them like the Ahlul Kitãb?
Answer: It is not permissible to deal in pork at all.

Question: Is it permissible to work at a store that sells pork in the sense that the Muslim supervisor asks one of his employees to give pork to the customer?
Answer: It is not permissible to sell pork, even to those who consider it lawful, be it directly or through an intermediary. As for handling pork for those who consider it lawful, there is problem in it; however, based on obligatory precaution, one should refrain from it.