I have installed several GM crate engines and have had success with them. Keep in mind that you still need to obtain intake & exhaust manifolds, carburetor, distributor, water pump, pulleys, flywheel, and other accessories which may cost another $800 to $1000. If you can find a complete running small block that may be the way to go. I have found in some cases that the cost of buying a used engine and having it rebuilt can cost as much or more than getting a crate engine and the related components.
Fred