Engine Oil Suppliment. Should be able to get it either from any parts store that is an AC/Delco dealer or the GM dealership parts department. Most guys use 2 bottles of it (I did).
For break in, you'll want to run about 2000-2400 rpm, varying the rpm during the process, for about 20 minuits. Don't let it idle at all. If you need to idle, shut it down, do whatever you need to do, then restart ( I had to do that, didn't put enough feul in the tank). Change the oil and filter. You'll also want to go through the valves.
