Bill:Those heads will not be a good performance head, regardless of valve size. The 1.78 valves would be the maximum size I'd try, the 1.94s would be badly shrouded by the chamber walls. Then, there's the port sizes. Smaller. And the compression ratio is low. This is not to say they can't be made into performance heads, but it would be easier to start with a better designed casting.
John in Selma, IN