This is hard. The only thing that can give you a definitive answer probably will be a full neuropych evaluation. If you go to some of the main children hospitals, your insurance often picks up most of the expenses.

Failing that, I would think the approach to his social deficits are going to be similar regardless of diagnosis. My son, who has no diagnosis, goes to a social skill group because his teacher thinks he needs to be more assertive and less timid in new situations, and one of the kids in his group has Aspergers. So ASD or not, they both benefit from the same group.