A frequent, sometimes heated topic of debate is upgrading to LED lighting in the headlight of vintage American Flyer, Lionel, or Marx trains. It shows how sometimes a little knowledge can be a dangerous thing. You have several options for LEDs in old electric trains, and not all of them are expensive or difficult.
Specialty retailers like Town and Country Hobbies sell screw-in replacement LED bulbs with an E10 base for vintage trains. It’s also possible to wire up your own circuit. You can also take your chances on cheap 12V E10 LED bulbs from Ebay.