Engine is rebuilt with only 2 hours break in time on stand. The freeze plugs in the block are leaking and I'm wondering what to replace them with(brass, steel etc.)?

Brass plugs and wipe a little permatex form-a-gasket (the fully curing version) in the block first.

Any idea what that's called so I get the right thing?

Should say 1B on the bottom of the tube.

I prefer steel ones, I think they grip the block tighter, yes they do not rust but mine will get changed out well before rust thru becomes an issue but many are totally happy with brass ones. I use the dorman brand which are much deeper than some of the shallow ones that are in the "pioneer" blister packed kits. I would use permatex #1(in the toothpaste tube).

I guess they weren't replaced when the engine was rebuilt? I like brass.
I rebuilt a 340 in 1986 and they rusted out last summer. I used steel then and put in brass last summer, wish I would have used brass back in 86.

I have seen Stainless steel ones....how do those compare?

The freeze plugs are new on my 440, but they leak. I went to Mazzolini's shop a few minutes ago and bought new ones, his are the deeper ones. I just looked at my 440 and it has the shallow ones. I bought another can of "The Right Stuff" and will put the new ones in tonight .

Sorry, brass.

I'll get over it

I had one rust out on me.
I was "lucky" it happened to be the one behind the exaust manifold on the drivers side.

Ok, I agree the brass plugs are better, but just wait till You need to take one of the "deep" plugs out. They are about 10 times harder to get out!
The stock ones just flip out when You use a punch on the edge of them.
Id rather use a brass short plug, if they are available anywhere.