Thanks for the question.
Block heaters usually take the place of one of the engines freeze plugs. If your car built with one, then I suggest buy on from a local GM dealer. Freeze plug heaters look like this...
There are some universal kits that are magnetic and can be secured to any metal surface. There are also oil pan pads that attach to the bottom of the oil pan to help keep things warm. This would be an easier route if you are wanting to do the install yourself.
Here is a really good one. This heats and circulates warm coolant through the engine. This will warm the entire engine and not just a small area...
I hope this information helps.