Just to add a bit - the Form 8050 is to transfer the registration. The pink copy says it's only valid in the U.S. (this is an FAA thing, not a Canadian requirement). This, presumably, is because the form is temporary and has not been vetted by the FAA yet. So the aircraft is not allowed to leave the U.S. (and FAA jurisdiction) until they've had a chance to approve the change of registration and issue a permanent registration slip.
As Hung said, the FAA doesn't care about ownership, only registration. In fact, I believe their paperwork still has wording to that effect ("registration cannot be used to determine ownership" or some such phrasing).
As a seller, make sure you also fill out and send in the change of ownership form that Hung posted a picture of earlier. This is the FAA version of turning in the plates when a car is sold. Sometimes the new owner doesn't register the airplane in their name right away. Or, if it gets exported to Bolivia (for example) they'll never tell the FAA. So it's always incumbent on the seller to tell the FAA that the plane has been sold.
It wouldn't hurt to do as Gerardo mentioned and write up a Bill of Sale and keep a copy for yourself. If nothing else, it'll help show the local taxing authority when the airplane left your possession so that you don't continue to get billed.
