A couple of years ago I sold a car on eBay for a few thousand dollars.
The procedure we used was to first let the purchaser inspect the car to see that it was as described. He had brought a bank money order with him to make the payment.
We then went to my bank and went to one of the desk people. The woman there looked up his bank on her computer and called the branch which had issued the MO. They verified that the MO had been issued by them and the amount of the MO and that it was valid.
We then deposited to MO in the bank and went to lunch, where we gave him the title and all the maintenance records. After lunch we went back to the house and got the car on the trailer he had brought and he drove off.
Your bank should be willing to look up the buyer's bank and make the call. Just make sure that the transaction is done on a weekday and that the banks will be open. Also, for protection, ask the person at your bank to look up the phone number on the internet and not rely on any phone number printed on the check or given by the purchaser.