Turns out old trucks are good for something … selling new technology.

This 1978 F-100 was equipped with two Eluminators to showcase the technology. (Ford)

Just days after Ford unveiled a 1978 F-100 pickup converted to electric drive using its new Eluminator crate motor for custom car builds, the $3,900 part has sold out.

The 281 hp motor is the same one featured in the Mustang Mach-E GT electric SUV and was originally listed in the Ford Performance catalog in August, but gained new attention courtesy of the F-100.

The Eluminator is rated at a maximum of 281 hp. (Ford)

The truck was a star of the SEMA (Specialty Equipment Market Association) Show in Las Vegas and features two of the motors, plus the battery and power controls from the Mustang Mach-E GT.

Ford Performance does not yet sell a battery and power controls, requiring builders to source their own, but said it would be adding them to the catalog in the future.

The Eluminator requires power controls and a battery to work. (Ford)

"That is coming soon from us, the ability to have a controller with the ability to calibrate it into your vehicle and then ultimately a battery pack," Ford Performance Global Director Mark Rushbrook told Fox News Autos.

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A Ford spokesman would not confirm how many Eluminators have been sold, but said that "demand has exceeded expectations" and that customers can sign up to be notified when the next batch arrives.