I think the only classes where there was a strong correlation with curriculum and grade achieved was Anatomy and Biochemistry. Microbiology is +/-, depending on how your school's curriculum is set up. Some students attended schools with nursing programs and it seemed that their microbiology courses were similar in structure to medical school, less as much information and the detail and knowledge required.
Immunology was another course where students said undergraduate work helped; a few students in my immediate group actually used the identical textbook and were able to reference undergraduate notes. The problem? We covered almost all of their undergraduate immunology course in two weeks, maybe less. Plenty of us did fine in that part of the course without an extensive background knowledge.
Of note about above, courses in medical school can be odd in that they will cover more or less of undergraduate subjects. Among my peers, almost all of us came to medical school with different majors and each of us had strengths, depending on background and the courses we decided to take before medical school. It was often that we'd be surprised by how fast medical school seemingly covered topics that undergraduate professors would seem to drone on about forever in a hope that the concept would be better understood. Sometimes things were explored in a more in-depth fashion in undergrad, but the overall conceptual understanding was still conveyed in medical school, i.e. relevant information. Similarly, some things were covered in tremendously more detail than was covered in undergrad. It really depends on the course. What makes medical school difficult is that you're learning many of the same concepts (and many new ones), often with additional information, at breakneck speed. You're expected to have the ability to quickly assimilate information.