matt wrote:
Does anyone know if this is possible?

A friend of mine did a TH55 (Hughes 269) conversion for the police
dept. he worked for. He had to go through an awful lot of paperwork and
flight testing. He said the FAA bent over backwards for him (probably
because it was for a govt. entity).

Bottom line is that you will have to work with your local FAA office
(US Govt in the phone book) ask for aircraft airworthiness and ask them
what you will be up against. They are the office that will wind up
working with you anyway.
Good luck,
Tom