5,1 115lbs recommended 300cc teardrop I want 345cc. Will 350cc look really fake on me? (Photos)

The dimensions are as or more important than the volume. Having said that, it appears that 350 range would be plenty full considering your desires and frame. Three hundred ccs would look perfectly fine as well but perhaps on the lower end of your desired range.

My best advice: more communication.
It is definitely worth spending more time (prior to the date of surgery) with your plastic surgeon to discuss further.  As you know, it will be important for many reasons, that you feel comfortable that you and your plastic surgeon are on the "same page" prior to proceeding.
Ultimately, careful communication of your goals (in my practice I prefer the use of goal pictures, direct examination/communication in front of a full-length mirror, in bra sizers, and computer imaging) as well as careful measurements (dimensional planning) will be critical.
Generally speaking, the best online advice I can give to ladies who are considering breast augmentation surgery ( regarding breast implant size/profile selection) is:
1. Concentrate on choosing your plastic surgeon carefully. Concentrate on appropriate training, certification, and the ability of the plastic surgeon to achieve the results you are looking for. Ask to see lots of examples of his/her work.
2. Have a full discussion and communication regarding your desired goals with your plastic surgeon. This communication will be critical in determining breast implant size/type/profile will most likely help achieve your goals. 
In my practice, the use of photographs of “goal” pictures (and breasts that are too big or too small) is very helpful. For example, I have found that the use of words such as “natural or fake look” or "D cup” etc means different things to different people and therefore prove unhelpful.
Also, as you know, cup size varies depending on him who makes the bra; therefore, discussing desired cup size may also be inaccurate. Again, the use of computer imaging has been very helpful during the communication process, in our practice.
3. Once you feel you have communicated your goals clearly, allow your plastic surgeon to use his/her years of experience/judgment to choose the breast implant size/profile that will best meet your goals. Again, in my practice, this decision is usually made during surgery, after the use of temporary intraoperative sizers.
I hope this helps. Best wishes for an outcome that you will be very pleased with. 

Thanks for the great question. Implant sizing can be one of the most difficult parts for the patent. Without knowing your measurements it's difficult to say which would fit you best. However, a general rule of thumb is that you increase about 1 cup size for each 150-175cc of implant. So a 350cc implant will take you up a little over 2 cup sizes. It looks like your practice is using Crisalix. This is a good program, but it tends to make the breasts look slightly larger than what they actually turn out to be. So if you like how a 300cc looks on Crisalix, you'll most likely like the 350cc in yourself. I hope that helps!Best,~Dr. Sieber