Probably a bit overkill, but I used a shore power socket (such as Marinco) for the block heater in my car; it will handle 250V / 50A:
Then a pigtail adapter can be used to adapt to your standard wall plug:
This is what it looks like on my car... it is the car's "nose":
This location was best for wire routing and it allows me to remove the bumper without needing to disconnect the block heater wiring.