Overheating 360 new engine

Ok here is what I have . The engine still got to 210 before I shut it down . Took about 25-30 minutes in the garage. This actually is double the time before the new pump. I recently was at a car show and I went digging into everyone’s cooling systems . They were all over the place . Water pump pulleys were all different sizes , radiators were different , stock fans electric fans, shrouds no shrouds, etc . I did talk to a few people at their cars and all said no overheating. As I stated a few pages back I have discovered the LS of the engine is hotter. Is it possible to have a head gasket upside down and still seal? How about using a magnum engine gasket on an LA engine? I haven’t had these apart enough times to know. Thanks again for the help.