I agree - I think that finding an expert tester who has experience with gifted kids who have autistic-like issues is crucial.
IQ testing aside, whenever I hear about or meet cases like this (almost anytime I hear "high functioning" autism) I would want to question/verify the original diagnosis, possibly by getting another opinion, etc. (e.g. there was one boy who went to our speech therapist right after our appt each week, and he was far more social than my kids, lol. I found it very hard to believe that he met the criteria for autism as set forth in the DSM-IV, which requires a severe lack of empathy, among other things). In these situations, I like to refer to The Mislabeled Child by Brock and Fernette Eide - there is an excellent chapter on autism and distinguishing it from other issues.
Just thought of something else - the child has good expressive language but not good receptive - that kind of raises a red flag for me that there's a possibility this could be an auditory processing situation rather than autism. I might expect the opposite from an autistic kid (in my very non-expert opinion).
It would seem that having an accurate diagnosis (autism vs. something else like auditory processing) might greatly affect what the most effective testing approach would be.
just my two cents
