Honestly, I think it depends on the prof...some don't mind turning a pre-req into a co-req. Anyways, I would email your organic/biochem professors and see what they recommend.
i found that bio chem concentrates a lot on mechanisms.. and going into biochem w/o having orgo... will certainly be tough since u won't have had any exposure to mechanisms
Depends on the particulars of your school's classes. As far as my school is concerned, I could have gotten away with taking them at the same time if I really needed to. Ask the professors.