Wait...here's a good answer.

Find a reseller that is extremely dedicated and offers mods, repairs, and break-in services. Pay the little extra for the peace of mind. You'll get an engine that's been inspected, broken-in, and tuned pretty close for your area. These guys exist solely to make guys as fast as they can be with minimal risk and worry.

Here are a few of the guys that are most active here on RCTECH, in no particular order. I apologize in advance for omitting anyone. There are many others.

Houston's Engine Service
Clockwork Racing Engines
EBMods