Used Engine Break In?

My 2000 Polaris XC SP 600 blew up a couple weeks ago. Figured out a crank rod bearing had a needle come out and into the cylinder. So I decided to go with buying a used engine. Picking it up tomorrow from a reputable dealer, and gonna put it in myself. My question is, for a used engine, obviously the rings don't need to be seated, but what do I need to do? Should I run premix through? If so what mixture and how much? I really don't wanna do a whole tank of premix if it's not needed, but if it's necessary I will. Here's the sled the engine is going in.


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Used Engine Break In?