Cylinder Head Gasket
The cylinder head gasket is the single more important gasket on the engine. Don't skimp on this one. The OEM one is about $30. Engnbldr sells a gasket kit for $30 which includes a Rock Product gasket. The kit is what I got originally. I came to my sense and bough an OEM gasket to replace it since I am spending so much on the engine. No point taking any chances.
I noticed two difference between the two gasket. The shape and reinforcement of both gaskets looks to be the same. The metal reinforcement on the Rock gasket does not lay as flat on the gasket as the Toyota one. It definitely needs to be re-torqued after some miles. The major difference is the the Rock gasket is lubricated with graphite on both sides. The OEM one is just lubricated on one side. The other side actually has a sticky coating. This is because the aluminum cylinder head contracts and expand at different rates than the steel block. There is movement between the gasket and the engine. It is preferable for the gasket to be sliding against the steel than the softer aluminum. The sticky surface against the aluminum head will make sure that the gasket only slides on the steel block. Is a good design feature Toyota has to make the engine more reliable.
If you are rebuilding the engine to go for a long time rather than a couple of years, I would definitely go with the Toyota head gasket for $30 more.