Viton push on seals is what I would and due use, not the old race Teflon type: tsk:
You need to know the outer diameter of the valve guide boss and the valve stem size as well as make sure the valve retainer or valve keepers do NOT hit the seal, minimum of .060 clearance at max lift works good for me
If they hit the seal it ruins them so they don't keep oil out of the combustion chambers
I usually buy mine from Goodson Tool and Motor supply, I don't have any of the better ones in stock so it is time to make up an order and restock now. I'm almost positive that the 440-1 heads have 11/32valve stem size valves in them form Indy, measure yours to make sure they haven't been changed
The two in the picture are not the really good race ones, they are more for standard street motor rebuild