New York State does not issue a title certificate for any motor vehicle of model year 1972 or older, travel or utility trailer that weighs less than 1,000 pounds, or limited used motorcycle (including a moped).
Info taken from this site:
http://www.nydmv.state.ny.us/broch/c19.htm
According to this, you should be good to go with no title. Maybe a notorized bill of sale?
If a MI title is required for the new owner, it would be his issue not yours, I believe.
I also found this on the Michigan DMV website:
Frequently Asked Questions
Vehicles
What vehicles are exempt from Michigan's titling and registering requirements?
Answer:
Every motor vehicle, trailer coach, and trailer driven or moved on public roads must be title and registered. Under Michigan law the following vehicles are exempt from titling and registering:
Passenger vehicles registered in another state operated by a nonresident for up to 90 days (new residents must title and register their vehicles immediately).
An implement of husbandry (farm tractors and equipment).
Any vehicle owned by the United States government.
A trailer weighing less than 2,500 pounds is exempt from titling but must be registered (a title may be issued on request). All trailer coaches must be titled and registered.
A vehicle driven or moved upon the highway using the most direct route (round trip) for the purpose of:
obtaining a weight receipt from a weigh master,
obtaining a physical inspection from a law enforcement agency, or
obtaining a salvage recertification inspection.
A moped is exempt from titling, but must be registered.
It looks like Michigan requires a title no matter what the age of the vehicle.
Not sure what your buyer would do in this case.