I can tell you that Ford cast iron welds very easily with 304 stainless steel ELECTRODES.
I was never convinced of putting anything into the ports by any means.
There were stainless steel "tongues" to install in the ports for a while also but seem to have disappeared and frankly I haven't seen these port stuffers for sale in decades either.
I prefer the heads to be a solid castings so nothing can come loose under any condition.