Inline 6 cylinder freeze plug part number

[88Ironduke]

I'm working on my 72' 250 and have a late model 78' head going on and I pulled the freeze plugs out of the head during clean up. The water jacket port measures out at 15/16" diameter. However it seems that finding these things on the shelf or as part of a kit is not as readily available as I had thought. I referenced Dorman 555-016 which measures out as that 15/16" but I don't have any solid part numbers to work from to say yea or nea on what to order.

Thanks
Paul