Pull a freeze plug, install heater....
Not trying to by a smartass, but if you are asking, you might wanna have someone else do it.
Or, look into a dipstick type heater element that you drop into the motor where the oil dipstick goes.
Anyhow, if you go with the freeze plug design, you'll have to remove one from the block, they are metal plugs press fitted into the engine casting, you remove them by drilling into them, then driving a tool (like a chisel) into the hole and prying them out. I assume the heater is contained in some kind of expansion plug that expands as you tighten it up?
Never seen one. Hopefully, I'll never live where I'd need one.
