I’m very surprised that you can get so many grades less than a B+ and still receive a 3.4-5 GPA overall. That’s still in range for a lot of accepted applicants. That said, Econ and Calc were the ones you really needed to do well in, so it’s probably not likely to happen.
If it were me, I would not do Econ major because since it screams “Ross Reject” (even if you’re going for a Econ PHd)
Some other options:
Majors:
apply to COE for Industrial Engineering
apply to School of Information
apply to Gerald Ford School
apply to Organizational Studies
apply to PPE (https://lsa.umich.edu/ppe/students/admission.html)
Minors:
Applied Statistics (I think it’s only 11 more credits)
Entrepreneurship
Ross minor
Complex Systems
You’ll most likely need to get a 3.6+ overall to get any decent internships/job offers.
You should also choose 1 or 2 relevant extracurriculars that requires significant leadership and project experience that you can talk about extensively in your resume/interviews.
Pay attention to this recruiting calendar listed for BBA. Contrary to belief, a lot of their official company recruiting posters do not list Ross BBA only and is open to all relevant majors. I only know this since I know a few IOE friends came to their events uninvited and nobody noticed or cared. For some reason, Ross likes to scumbag people into thinking some resources/events are Ross only but really are not.
https://www.bus.umich.edu/impact/Calendar/displayCalendar.asp?query_ord=2&layout_mode=0&layout_view=2&jump_date=2/7/2016
Pay attention to Handshake events. Apply to their jobs.
https://careercenter.umich.edu/article/handshake
LSA Internship Events
https://umichlsa-csm.symplicity.com/students/index.php?s=home
Even though the UMich CareerCenter is considered weak compared to iMPact and EnGenius, you’ll have to leverage them the best you can. Visit them multiple times to review drafts of your Resume/Coverletters and practice interviewing especially with different advisors.
Register for WetFeet.com and Vault.com
Look for other career/interview prep books on amazon.
Participate in events where you get accolades/awards such as case competition, pitches, etc…
Some Ross clubs have their own internal recruiting events you can attend as a non-Ross student.
http://michiganross.umich.edu/our-community/students/clubs-organizations/browse-all
Other things:
Having a personal website (hosted on your own domain) can go a long way if you have great artistic and writing skills that reflects your personality very well. Put it at the top of your resume near your email/phone#
Befriend a few Ross BBAs who may to give you insider information info on opportunities (haha).
I’ve known a few Psych/Comm/PoliSci grads that did somewhat of a combination of the stuff above and got good offers and even working alongside some Ross grads as the same role. That said, you’ll have to work harder than them to get the same results.
Goodluck