Is 450cc too big for my body?

In general, 450 cc implants are on the bigger side for a 5'0 foot person.  Cup sizes are not standard across bra makers, and implant sizing is NOT based on height, weight, BMI, or capsize.  This is something you will need to do IN PERSON with an experienced surgeon to determine what works well for you, and to get advice about if what you like is possible and what to expect with regards to results.  Be sure to discuss your goals and concerns with your board certified plastic surgeon and consider the pros and the cons. Be certain your surgeon is properly certified.  I've attached a link where you can start your search. 

Hello and thank you for your question. Congratulations on your upcoming surgery.  450cc may be a large implant for your frame.  The size, profile, and shape of the
implant is based on your desired breast size/shape, your chest wall
measurements, and soft tissue quality.  This decision should
be based on a detailed discussion with equal input from both you
and your surgeon. 
Best wishes and good luck.
Richard G. Reish, M.D.
Harvard-trained plastic surgeon