Will I be adequately prepared for the biochem portion of the MCAT if I take chem 351 instead of mcdb 310?
Yes, you should be. Chem 351 is known for being more in depth than the latter introductory biochemistry courses offered to undergrads. It’s particularly useful if you’re pursuing a biochemistry degree I believe. This link will lead you to a blog-post comparing different pre-med courses offered at UMich; you can find a comparison of CHEM 351, MCDB 310, and BIOLCHEM 415.
Good luck with scheduling!