Just a quick thought, but if you believe a) that we should base policy on what people do (revealed preference) rather than what they say and that b) economic analysis can be applied to political activity (public choice theory), doesn't that suggest that fascists are right-wing, and/or that they believe they are more likely to succeed if they work with conservatives?
I mean they might claim that they are 'national socialists' or 'beyond left and right', but in practice (revealed preference) fascists historically have allied with conservatives, not the Left, and that's where the overlap in supporters seems to be too. And if fascist politicians are following their own self-interest in their political activity, as public choice theory suggests, they must think that they get more change out of conservatives than lefties too.
I'm not claiming that this proves that fascists are right-wing. In practice people define fascism in terms that ensure that it ends up on the other side, and as a lefty I do think they are right-wing. But if you put a lot of store in revealed preference and public choice theory surely you should be pulled in that direction too.