Hot Rods 331 hemi 1955

Does anyone know what size freeze plug goes in the end of the rocker arm assembly or what other car they are used in so I can find them at a local parts store?

 

Anyone?

 

You can get a set from Bob Walker at Hot Hemi heads.com they are not expensive.

 

I was hoping to get some today

 

Anyone else?

 

dorman #555011 5/8's cup plug

 

Thanks know I can go to a parts store with a number!