Safest
When I had a car and trailer for sale in the 40K range, several people tried to buy it, and a few were scammers/traders.
The guy that did it right, talked to me over the phone several times and asked for detailed pics from me. He then flew in fom California, spent the day with me getting to know me. He took more detailed pics of the car, trailer, my residence, my drivers license and other identification and the neighborhood. We also went the bank, a couple of my friends, the chassis shop the car was built at, and a notary and got a signed deal notarized.
He returned home and did more research on me and the origin and history of my car to help him decide I was trust worthy and the car was worth the asking price.
He then sent United States Postal money orders to me on a routine basis until all but 5K was paid. Then his buddy drove in from Kanas and inspected the car based on the pics taken previously and talked to him on the phone as to everything being correct. Also his buddy was buying the trailer once it returned to California, so he had a vested interest in the deal too.
Then he paid me the final money owed and I gave him a bill of sale with no price on it.
I think we both got what we wanted and still talk to this day.
That car is the RED LINE OIL Super Gas/Super Comp car at NHRA division 7 and national events