optimally, earlier is better, but if you apply Mohs, I’d start looking in fall or so of Pgy4. You can be in the process as you apply mohs. If you don’t match, just continue the process and sign on if you find out you didn’t match. That way you’re not trying to back out of a contract. So get a jump on it, but just don’t sign anything until you know about mohs.
Lots of people don’t land their forever job right off the bat, so not a huge deal.