A question and an ask SBM 318

Hi Steve, I'm not sure of its dimensions since its waaaay up inside the block. From my quick and dirty research it appears it's a 9/16" plug. With a flashlight I can see the shoulder. But cannot get a caliper on it. The blueprint drawing has a PN. Probably $30 from the dealer lol. it looks like that one plug doesnt come in the kits. Can you check its dimension?

Frosty the punk,
Mark is a good friend. He has a bunch of this stuff kicking around his shop. As I stated I dropped it off a little over a year ago, paid it in advance, and told him whenever you get it done. No rush. I stop by to visit after work and talk about stuff. Never badger him about my engine. Asking him about the bigger core plugs is not a big deal.

Rumble, I have only 1 of those front plugs. I think it was stamped 19/32" I still need the second one.