What spark plugs do you need for a high performance Chevy small block?

Rule of thumb. Before 74, Autolite 76, or any cross referenced plug to that. After 74, 26. You will have to lok to tell for sure, because so much small block stuff interchanges. Look at the seat in the hole. If it is tapered, then the 26. If it is flat, then the 76, with the washer.