Personally I wouldn't talk with anyone at the FSDO level. They are not the experts. Talk with Airman Certification Branch in Oklahoma City. They are the experts. They deal with every day.
And according to the Foreign Certification desk in Oklahoma City, to do an FAA ATP checkride all you need is the validation letter from the FAA. Which you get at the FSDO. If your national medical is current, you do not need the FAA medical exam. If it is not you will need to have a minimum of a FAA 3rd class medical. Reference FAR 61.153 (c).