I ordered a "dry" type block heater for my 5.7L Tundra. This means you do NOT have to drain/refill the antifreeze and there is no chance of leaking coolant, as this heater does not immerse in the coolant. The hole for installation is present on all of our motors, it's as simple as buying the $30 part and spending 30 minutes installing it.
Here's the link for ordering the block heater:
00213-00900 - Toyota Block Heater (see description) Parts and Accessories
You will only need 1 tool for this installation, and that's a pair of wire cutters for clipping the ends off the zip ties you use when routing the wires. You'll also need some zip ties as there are only 6 included with the block heater and I didn't think that was enough.
All of the photos of the install process are at the end of the post. The first several pictures are to get you oriented so you can locate the hole for the block heater, and the last couple show how I chose to run the power cord.
Step 1: open box and make sure you have all the necessary parts (heating element, power cord, thermal grease, zip ties).
Step 2: lie down next to the driver's side door, with your head towards the engine.
Step 3: slide under the truck and locate the exhaust on the driver's side of the engine. Just behind the header you'll be able to see the hole for the block heater.
Step 4: you'll see an electrical connection mounted just beneath where you need to work. Pull the connector off the metal mounting bracket to allow yourself a little extra slack in the cables so you can squeeze your hands further up.
Step 5: once you've located the hole for the block heater, go ahead and liberally apply the thermal grease to the heating element - be sure to not get any of the grease on the prongs that the power cord hooks onto. Now put the rest of the grease (should be about 1/2 the container of grease) directly into the hole on the engine. My only tip for making this easier is after applying the grease to the heating element, cut the entire end of the grease packaging off so that it comes out very easily (because when you jam your hands between the exhaust and the engine there isn't much room to be trying to squeeze the grease tube).
Step 6: put the heating element into the hole, but be sure and make note of the alignment of the clip on the heating element and the spot on the engine block where the clip will hook to. You'll be in an awkward position with your arms shoved above your head and not able to see anything, but keep at it and you'll finally get the heating element in the hole. At this point the block heater will slide into the hole, but because it is a snug fit and a blind-ended hole, the pressure inside the hole will keep trying to push the heating element back out. I found it easiest to force the element all the way in the hole by using only my right hand, with my palm against the engine and my thumb on the end of the heating element. Again, no really easy way to do this, just find some body position that allows you to apply enough force to clip the element into place.
Step 7: come back out from under the engine, and feed the power cord down from the engine bay. You're trying to drop it as close to the heating element as possible, so the closer to the fire wall you can drop the power cord, the better.
Step 8: return to underneath the truck, and plug the power cord onto the heating element.
Step 9: route the power cord. Be sure and start with the portion of the power cord that is closest to the heating element, and work your way toward the front of the truck. I know that seems like common sense, but I was so anxious to find a place to mount the standard plug in the grill that I ended up with my power cable running over a coolant hose that I would have rather had it running underneath. No big deal and it's not going to affect anything, I just would have preferred it the other way.
Here are all the images I have:
I will have to pop the hood every time I want to hook up the heater, but that doesn't bother me, as I was more interested in making the plug as hidden as possible.