If it's installed in place of a freeze plug, you should be able to replace it without any problems. The photo is a little fuzzy- - - -is the spring and the bracket below it attached to the part, or is that an optical illusion? Most block heaters will have an electric wire attached that would be plugged into an extension cord when the vehicle is parked overnight in sub-freezing temperatures. The cord might have been cut off flush with the heater but there should be enough of it remaining to see where it used to be.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!