I have a 1979 F150 with a 300 I6. The motor is BRAND SPANKIN NEW. I have run about 3 oil changes through it with regular conventional oil. I am wondering if i should switch to synthetic or not? Money isn't really the issue it's just being that it's so old and i'm not sure if it's safe to run synthetic in older engines. (Even though it's brand new) I am either going to put in Amsoil, Royal Purple or Mobil 1. Can ya help?

 

I don't see any reason that a modern synthetic oil couldn't be used. The engine is freshly rebuilt/new, so it should be spotless inside, and all seals made from more modern materials that are formulated with these lubes in mind.
Older seals were an issue with older synthetics. Not much of an issue, these days.