TrueWest wrote:

There is a brass adapter which has been "leaded" into the cast iron
hub in the stack fitting. The "football" is lead which has been
wiped over the connection.

You can drill out the lead by making a series of 1/4" holes around
the circumference. Then pry out the lead and the Oakum behind it.
That will leave the raw cast iron hub. You can then get a "donut"
rubber adapter which will connect PVC to the hub.

It's also possible to leave the brass adapter in the hub and use a
FERNCO No-Hub coupling over the end of the adapter sticking out.
You may have to remove the wiped "football".

Jim

Thank you very much.
Id prefer to leave the adapter in. What's involved in removing the
wiped "football"? Just a chisel and some elbow grease?

Yes, perhaps a hacksaw to cut thru the lead in several place;
that will allow the chisel to "peel" it off. Rasp to file the
roughness left.
Jim