I posted in /r/cosplay a costume I've been working on trying to make a 'Historical' Thor. I've been solely using Wikipedia as a source, which potentially dates the god of Thor back to 2-3rd century. I'm assuming this god was based on a human at some time prior to this, what would this human look like? It seems like needed features are a belt, gauntlets/gloves, a possibly large hammer and red hair and beard.
That's not really how things like this work.
Thor is really the 'Germanicization' of a proto-Indo-European god of thunder. There wasn't a human that Thor was based on any more than there is a human that Cernunnos the Celtic Horned God is based on or Hades, or Ganesha, etc.
What would he look like to be most 'accurate'? As with most gods, probably a lot like his followers. In this case a Germanic warrior with a hammer is about as close as we can get.