Paypal, not using "Friends and Family", but regular payment, is among the safer ways for a buyer to pay for an item to a private seller. If the seller flakes, and doesn't have proof of shipment, the buyer can get their money back. This comes with a small fee. When a seller balks at the fee, offer to pay for it. If they cite some other reason for PP F&F, (one common example is income reporting) consider that a clue they may be dishonest.
As a seller, make sure you take images of the item in the box and with shipping label, and always use tracking. I've thwarted a few would-be swindlers filing claims with Paypal that I didn't complete shipment, and having a little proof on my mobile phone is all I need.
Other forms of payment, cash, personal check, money order, cashier's check, Venmo, Paypal's Friends and Family, rely on the seller's honesty and the buyer's faith to work. If the seller flakes, or the payment is fraudulent, there is little practical recourse.
Heavy parts are not practical to ship. In many cases, shipping costs or hassle outweigh the cost/value of the item. But not always. A bigger $$$ item may be worth the hassle setting up freight, or meeting the buyer halfway.
Swap meets are among the best places to unload heavy car parts.